Why not synthetic oil??

[rothsean]

So why does DMC say not to use synthetic oil? What does it damage?

[WelmoedJ]

Your engine has worked a long time and doing so collected some dirt.
Starting to use full synthetic oil in an old used engine may start a cleaning session.
Such a cleaning session may clog your oil channels and that could be the beginning of the destruction of your engine.


On the other hand, if your engine is crate new, you can start using synthetic oil.
Brand new, nothing to clean, so usually no problems.

[Mark D]

I believe it was Dave S. who coined the phrase "Delicate Balance of Crud".

You do not want to upset this delicate balance and have years worth of particles come loose and start floating in your oil and causing damage. Synthetic oil also has much smaller molecules than conventional and will leak in areas where conventional oil will not, again, partialy due to the crud being gone that was once blocking leaks.

[Michael]

I have also subscribed to the theory that newer engines have much tighter tolerances than older engines. Synthetic may cause oil consumption issues in engines that were not designed for it. My car had a crate engine installed that had been taken down for a stage II package before the first mile was put on it. I still opted for (thick) conventional oil(20-50) over synthetic.

[LEVY]

I don't believe syntetic have better detergents than regular, high qualty oils. You can try them, if you don't see leaks, you are good to go. If you do see leaks, tben back to fhe old stuff, no harm done.

LEVY

[andy blackmon]

I have had synthetic oil in my Delorean for over 10 years, with no problems what so ever. I have 4 cars and all are on synthetic oil as is my lawnmower, I tend to go a bit long between changes and with you synthetic you can, case in point '98 F-150 with 240,000 miles does not use oil, runs great and get 10,000 mile oil changes.

[David T]

The main advantage to using Syn is extended oil change intervals. For that you pay a LOT more for the oil. Since most of us do not put a lot of miles on the cars anyway it isn't worth buying an oil you don't have to change for 10 years! The motor was not designed to take full advantage of all of the benefits of Syn anyway. Once you start using a mineral-base oil and then switch the seals won't like the switch to Syn and may leak. Bottom line, use the best oil you can (mineral-based) and change it often (once a year).
David Teitelbaum

[LEVY]

That is not true, it is just a myth.

You should change syntetic oil as often as regular oil. The main advantage of syntetic oil is better protection, not a longer life!

Use syntetic oil if you can aford it.

LEVY

Often, once a year?

Some people use Delorean as daily drivers!



The main advantage to using Syn is extended oil change intervals. For that you pay a LOT more for the oil. Since most of us do not put a lot of miles on the cars anyway it isn't worth buying an oil you don't have to change for 10 years! The motor was not designed to take full advantage of all of the benefits of Syn anyway. Once you start using a mineral-base oil and then switch the seals won't like the switch to Syn and may leak. Bottom line, use the best oil you can (mineral-based) and change it often (once a year).
David Teitelbaum

[DMC3165]

That is not true, it is just a myth.

You should change syntetic oil as often as regular oil. The main advantage of syntetic oil is better protection, not a longer life!


You are partially incorrect. I spoke with a customer service rep from Mobil a bunch of years back about this. Mobils recomendation with synthetic oils is to follow the maximum oil change interval that your engine manufacturer suggests. At the time Most engine manufacturers had a two tier service schedule one for regular driving and one for severe service. At The time the Chevy I owned had a 3000 mile severe service schedule and a 7500 mile maximum service interval. The 7500 is what they recommend.

[LEVY]

Ok, but you are not telling me that they told you to go over 7500 ml. if you use synthetic. You still on the regular oil range!
Combustion causes any oil to be contaminated.

Synthetic oil may last longer but you still need to change it due to contamination.

LEVY


You are partially incorrect. I spoke with a customer service rep from Mobil a bunch of years back about this. Mobils recomendation with synthetic oils is to follow the maximum oil change interval that your engine manufacturer suggests. At the time Most engine manufacturers had a two tier service schedule one for regular driving and one for severe service. At The time the Chevy I owned had a 3000 mile severe service schedule and a 7500 mile maximum service interval. The 7500 is what they recommend.

M

[nullset]

Actually, in the US, "synthetic" oil doesn't mean anything special. Some oil makers sued for the right to call their dino oil synthetic, and won.

So yeah, be careful out there.

--buddy

[Dangermouse]

The computer in my DD Mercedes tells me to change the syn oil at 13,000, or every year, whichever comes first.

[Michael]

The computer in my DD Mercedes tells me to change the syn oil at 13,000, or every year, whichever comes first.

Not to go too far off topic but I should warn you not to put too much stock in the Flexible Service system. FSS was designed to do one thing, reduce ownership costs to prospective buyers. As a former service manager for Mercedes Benz, we constantly saw cars going south due to lack of service...especially transmissions. We recommended every 5k miles for synthetic oil changes(class A service) no matter what FSS is telling you, and 50k miles for transmission services as opposed to 100k(which on some were unservicable due to the torque converter being sealed). I left Mercedes in 2003 when FSS was just getting it's feet wet so much may have changed since.

[David T]

All of the auto manufacturers are trying to increase the service intervals. On the one hand it is better because people forget and don't service as they should. On the other hand it is very BAD because if you do skip on an extended service schedule it is a LONG time till the next one! The EPA is the driving force behind this, they are working their way up to a motor that will meet emissions for 100,000 miles with the least amount of service possible. This is some of the thinking behind the use of Ethanol (the motor runs cleaner) and now the push to remove heavy metals from oil (they contaminate the catalytic convertors). The EPA already go the Lead out of the fuel. Oils not only get contaminated, they break down and the additive package gets used up. The filter is supposed to remove the contaminants but the oil breaking down can only be overcome by regular replacement. The additive problem can be overcome by replenishing additive but you could overcompensate and that is just as bad. Regular, frequent replacement is still the best option but again, the EPA. By extending oil change intervals there is less oil to dispose of. One of their goals, to reduce the amount of hazardous waste. The service intervals recommended by the auto manufacturer are created based on some assumptions. One is the # of miles used per year. A typical # is 10,000 miles. As you can see if you have a car that you do not drive a lot you have to make up your own service schedule. Usually if you do not hit the mileage required you just change teh oil and filter annually.
David Teitelbaum

[Dangermouse]

Not to go too far off topic but I should warn you not to put too much stock in the Flexible Service system. FSS was designed to do one thing, reduce ownership costs to prospective buyers. As a former service manager for Mercedes Benz, we constantly saw cars going south due to lack of service...especially transmissions. We recommended every 5k miles for synthetic oil changes(class A service) no matter what FSS is telling you, and 50k miles for transmission services as opposed to 100k(which on some were unservicable due to the torque converter being sealed). I left Mercedes in 2003 when FSS was just getting it's feet wet so much may have changed since.

It's a moot point my my case, as the "year" came up well before the 13k - actually at about 5k. Due a class B service (which as you know, is basically an oil change and a bunch of checks) which the dealer wants the guts of $400, somewhat contrary to the "reduce ownership costs" thing.

My point was that those Germans recommended > 7500 miles (on Mobil1). It would be interesting to run the next one to 13000 and get an oil analysis done and compare it to my 2010 Caravan, whose FSS bings at 2400 miles (at which point it is already a quart low) on dino oil. Both ~50,000 mile cars.

[David T]

Changing based on oil analysis is the "gold standard". The problem with that is it costs more to to the analysis than to just change the oil. There are many other benefits to doing analysis though. For ordinary automotive usage where breakdown, service and repair is not critical it doesn't make economic sense. It is done by large truck fleets, aircraft, and the military where things are more "mission critical". As for the Delorean, it makes the most sense to change the oil and filter every 5,000 miles or once a year. A tune-up once every 10 years or as required if it is not running right. Best measure of "running right" is to watch your gas mileage. If it starts to decrease it is time to tune up. Batter every 5 years, tires every 7 years. Brake and clutch fluid every other year. Test the anti-freeze every year for ph and strength. Once a year inspect the undercarriage, grease and check the brakes, C/V joints, TABs, oil levels, etc. This is all assuming the car is in otherwise good shape and running well.
David Teitelbaum

[Bitsyncmaster]

The oil change indicators in my daily drivers go about 10,000 miles. I think all they do is time engine idle time, miles driven and maybe some other conditions such as WOT. I don't think any sensors monitor the viscosity, contamination or composition of the oil.

I have always used MOBIL 1 in my D. Never had any leaking engine oil even running 10-30. I tried the 20-50 but have gone back to 10 40 now.

[LEVY]

So, to answer OP questions:

1.- We don't know.
2.- No damage done by using synthetic.
3.- Use it if you can afford it.


LEVY


The oil change indicators in my daily drivers go about 10,000 miles. I think all they do is time engine idle time, miles driven and maybe some other conditions such as WOT. I don't think any sensors monitor the viscosity, contamination or composition of the oil.

I have always used MOBIL 1 in my D. Never had any leaking engine oil even running 10-30. I tried the 20-50 but have gone back to 10 40 now.

[DCUK Martin]

The main advantage of syntetic oil is better protection, not a longer life!


...and the PRV is hardly a highly engineered tuned engine, it'll last hurdeds of thousands of miles with regular changes of the cheap stuff

[SIMid]

I read somewhere that if you go fully synthetic, you can't go back to regular oil.

[lindbergh]

There is a lot of misinformation about synthetic oil. In the US as previously mentioned most oils labeled as synthetic are not, it is simply highly refined dino oil. The term synthetic in the US is a marketing term and has little to do with the makeup of the oil. Basically, if you are not paying around 10 bucks for a quart, then it is not true synthetic. There are only a couple of manufacturers that produce true synthetic oil. As far as detergents (HD oils), all high quality oils are high detergent (HD). There are not "special" detergents in synthetic oil, its the same stuff. So unless you have been using non detergent oil, then synthetic is fine in most cases. If you are using non detergent oil I would be careful switching to synthetic or HD conventional oil. The main draw to synthetic is it does not break down as fast as conventional oil, it also has a slightly lower coefficient of friction. For this reason I would not use synthetic during the break in period of a new or rebuilt engine. Conventional oil and synthetic oils are fully compatible, you can mix and match it any way u want, just keep the weight of the oil the same in your mixing an matching. You can buy hybrid synthetic which is just that, some conventional dino and some highly refined dino. I have not seen any true synthetics as hybrids but they are compatible with all conventional oil. If you switch to synthetic and you get seepage from the seals, you can switch back to conventional with no problem.

BTW, I am new to this forum, and looking forward to getting my D delivered early next week. This is a cool forum.

[Spittybug]

There is a lot of misinformation about synthetic oil. In the US as previously mentioned most oils labeled as synthetic are not, it is simply highly refined dino oil. The term synthetic in the US is a marketing term and has little to do with the makeup of the oil. Basically, if you are not paying around 10 bucks for a quart, then it is not true synthetic. There are only a couple of manufacturers that produce true synthetic oil. As far as detergents (HD oils), all high quality oils are high detergent (HD). There are not "special" detergents in synthetic oil, its the same stuff. So unless you have been using non detergent oil, then synthetic is fine in most cases. If you are using non detergent oil I would be careful switching to synthetic or HD conventional oil. The main draw to synthetic is it does not break down as fast as conventional oil, it also has a slightly lower coefficient of friction. For this reason I would not use synthetic during the break in period of a new or rebuilt engine. Conventional oil and synthetic oils are fully compatible, you can mix and match it any way u want, just keep the weight of the oil the same in your mixing an matching. You can buy hybrid synthetic which is just that, some conventional dino and some highly refined dino. I have not seen any true synthetics as hybrids but they are compatible with all conventional oil. If you switch to synthetic and you get seepage from the seals, you can switch back to conventional with no problem.

BTW, I am new to this forum, and looking forward to getting my D delivered early next week. This is a cool forum.

Welcome to the group Lindbergh and thank you for your comments. Do us a favor? We are trying to become a more "civil" group of people (for the lack of a better term). We recognize the challenges of spirited debate via the anonymity of the web and the temptations for some to troll. Many of us are trying to personalize the experience a bit more and are signing our posts with our real names. You can do this via the control panel settings. We also ask members to put at least a general indication of where they are located as this makes it much easier to offer assistance or to put you in touch with another local owner should you need help.

I'm sure some will ask your qualifications to explain the above. Are you in the business? Oil generally isn't a hobby after all!

[lindbergh]

Thanks! ^ Will do.

[DMCVegas]

After reading this thread and having to have my state inspection for our truck done today, I decided to ask the owner of the garage a few questions about synthetic oil. This is what I got back.

Synthetic oil is perfectly fine to run in older engines, HOWEVER there are a couple of caveats.

If the engine has been perfectly maintained and never went over mileage or time on ANY of it's oil changes, it's perfectly fine to go directly to synthetic and the synthetic maintenance schedule.

If the engine has NOT had a perfect maintenance history, or if you're unsure or just don't know, you need to bring it over gradually by doing about 2 oil changes with synthetic every 3K miles. For really bad engines you might need to use a synthetic blend with that first oil change. After that you can go onto the synthetic schedule of about 6K-7K depending upon driving, but that's it. He said that this was because synthetic would indeed break allot of the debris loose around the internals of the engine during those initials runs filling the filter and contaminates the oil itself quicker.

He also sold Royal Purple in his shop and I asked him about that too. He said that he was a big fan and cannot recommend it enough. But that he would especially NEVER advise a direct switch over to RP even on a perfectly maintained engine. He said that RP has extra detergents in it that work VERY well, but on a non-synthetic engine you run the risk of clogging the sump and damaging the engine even on those perfectly maintained engines that have only ran conventional oil.

The other thing about Royal Purple is that while it can go for 10,000 miles before having to be changed, you still have to replace the oil filter every 5K miles and top off the oil. You could get away with not doing it in a car that only ran highway miles, but for any vehicle used for commuting, towing, or hauling, you absolutely must change that filer.

Not my 2¢, but an interesting outside opinion of another professional mechanic that I found.

[LEVY]

One thing for sure, the more you ask, the more different answers you will get.

I remember back on the 70's, the first synthetic oil was available to the general public or end users, however you want to call it.

It was made from jojoba seeds if I recall correctly.

It was called Synthetic because it was not petroleum based but was made from vegetal products. It was weird because back then clothes made from petroleum products and not from natural fibers like cotton, wool and silk where called "synthetic", go figure!

So as someone before noted, nowadays synthetic means nothing really!


LEVY

[mnoeltne]

First I would like to say that I have been running Mobil 1 synthetic in my DeLorean since 1999 with no problems at all. No sludging, no leaking seals. No problems.

Secondly, the extra cleaning power of synthetics that was mentioned in a couple of posts above is now a moot point. The new API SN spec for oils calls for an additive package that gives regular oil roughly the same cleaning power as the older synthetics. Even the SuperTech house brand oil at Walmart is now SN rated and has those additives. So any oil you buy will clean your motor. If you have a dirty engine, you probably ought to do a couple of short oil change intervals using a SN rated oil to get it cleaned out before going to a longer interval.

In modern cars oil contamination is not as bad as it was years ago. EFI and computer controls really cut down on combustion contaminants that would otherwise end up in the oil. Not as much fuel getting there either since the fuel delivery is so much more efficient and precise. Synthetics DO allow longer oil change intervals on modern engines compared to regular oil. Lab analysis has shown this many times. Synthetics also offer much better protection under more extreme conditions like turbo engines.

But really, if you change oil at anything less than 7500 mile intervals, and you don't race or run a turbo, then any modern oil will protect your engine well. I really don't need to run Mobil 1 in mine, but I run it in other cars I own that are operated in conditions where a synthetic is better, so it's more just habit to run it in all my cars now.

[DMC3165]

As a personal opinion on this topic. I prefer not to tempt fate on this subject. My D has run fine on regular oil since 1998. Only about 2 years ago I switched to Diesel oil spec CJ-4 in the D for the additive package. I was thinking at the time our engines were built there were no synthetic oils but there were higher levels of ZDDP in regular motor oils. The CJ-4 spec oils are ideal for gas engines of our vintage. Too many changes in engine design have happened in the last 30 year's that are focused mainly on fuel economy and lower emmisions then engine longevity. A lot of modern engine manufactures routinely call for lighter oils so there is less drag on the motor during operation and higher temps to burn off more hydrocarbons. This doesn't necessarily offer the best level of protection and in addition most engines built today will be recycled into soda cans 30 years from now.

[DMCVegas]

As a personal opinion on this topic. I prefer not to tempt fate on this subject. My D has run fine on regular oil since 1998. Only about 2 years ago I switched to Diesel oil spec CJ-4 in the D for the additive package.

What is the weight equivalency of that oil? Back in Vegas furring the summer I would run 20w50 when the temps were sustained triple-digits. But come fall as the temps got cooler you could definitely hear the engine having a hard time turning over on cold mornings, and gas mileage was impacted.

[DMC3165]

What is the weight equivalency of that oil? Back in Vegas furring the summer I would run 20w50 when the temps were sustained triple-digits. But come fall as the temps got cooler you could definitely hear the engine having a hard time turning over on cold mornings, and gas mileage was impacted.

15W-40 and I've had no problems in colder weather. I generally run the car regularly (twice a week) until the temps are well below freezing or until there's salt and snow on the ground. Then the battery comes out, and its usually no longer then a month.

[sdg3205]

I've been giving some thought to switching 3205 over to synthetic oils.

Over on the Miata.net forum, there is overwhelming support for the use of synthetics in both engine and transmission/differential. Overkill? Maybe, but considering the sample size of about a million miatas, most with over 150,000 miles, it's hard to refute.

I put about 2,000 - 3,000 miles on my car every year, which is virtually nothing and results in 1 oil/filter change per year, typically near the end of the driving season. I've been using Castrol 20w-50. The car sleeps from November 1st - March 31st. Mobil 1 makes a 20w-50, but it is allegedly geared towards air cooled bikes. Their next closest synthetic is a 15w-50.

As far as the transmission is concerned, Motorcraft MTF full synthetic is praised by almost everyone. No idea if it would make an ounce of difference in our transaxle though. Would it even be compatible?

[David T]

I've been giving some thought to switching 3205 over to synthetic oils.

Over on the Miata.net forum, there is overwhelming support for the use of synthetics in both engine and transmission/differential. Overkill? Maybe, but considering the sample size of about a million miatas, most with over 150,000 miles, it's hard to refute.

I put about 2,000 - 3,000 miles on my car every year, which is virtually nothing and results in 1 oil/filter change per year, typically near the end of the driving season. I've been using Castrol 20w-50. The car sleeps from November 1st - March 31st. Mobil 1 makes a 20w-50, but it is allegedly geared towards air cooled bikes. Their next closest synthetic is a 15w-50.

As far as the transmission is concerned, Motorcraft MTF full synthetic is praised by almost everyone. No idea if it would make an ounce of difference in our transaxle though. Would it even be compatible?


As you can see from the previous posts most people's choice is anecdotal and not based on a lot of long term experience with many cars. Bottom-lining the subject, you can use whatever you want as long as you change it on a regular basis. Better oils allow longer service intervals if you want to extend them. For a car driven less than 10,000 miles a year you are probably best served by changing the oil and filter annually whatever you use. If you want to go for a better oil for the transaxle try Redline MT-90, that is what they use in Lotus's with this transaxle and a LOT more horsepower. As for viscosity, check the Owner's manual for the recommended rating for your area and temperature. Syn oils were developed for much longer intervals, tighter fitting engines, roller cam followers, reduced metal additives, and higher operating temperatures such as with turbochargers. Because they are "created" all of the molecules are very close to the same size so if you have any leaks, the leaks tend to leak more since there are no "large" molecules among the small ones. Most mechanics will say if you have old seals you should not use a Syn oil. Old seals do not seal as well as new ones and will tend to leak more. Whatever you use in the transaxle it MUST be rated GL-5. That does not need to be changed very often but the level should be checked at least every 10,000 miles or once a year. Do not forget that the brake fluid should be changed every other year.

[Hokie]

There are so many threads related to motor oil I wasn't sure which to use. Here goes: I've always used Castrol 20W-50 as that seemed to be the consensus of numerous long term owners. I'm told that Castrol used to publish the amount of zinc in their oil but then stopped doing so, leading many to believe that the zinc level has gone down below what is needed for our flat tappet cam engines. So I had some time today and I called Castrol. Here's what they said. They do NOT provide data on their oils because it's proprietary info. Furthermore, the ONLY oil they manufacture specifically for classic cars needing sufficient zinc is Castrol Edge 5W-50. That's it. The only one. And it's a full synthetic. I'll also add that a highly respected DeLorean guru recently told me he recommends and uses Castrol 15W40 DIESEL oil. I read through a few varying opinions on diesel oil usage on this forum, but this guy definitely knows what he's talking about. SO - I'm still concerned about my cams and can't decide which oil I'll use for my next oil change. My gut says go with "the guru." Question: has anyone used the Castrol Edge 5W-50?

[David T]

There are so many threads related to motor oil I wasn't sure which to use. Here goes: I've always used Castrol 20W-50 as that seemed to be the consensus of numerous long term owners. I'm told that Castrol used to publish the amount of zinc in their oil but then stopped doing so, leading many to believe that the zinc level has gone down below what is needed for our flat tappet cam engines. So I had some time today and I called Castrol. Here's what they said. They do NOT provide data on their oils because it's proprietary info. Furthermore, the ONLY oil they manufacture specifically for classic cars needing sufficient zinc is Castrol Edge 5W-50. That's it. The only one. And it's a full synthetic. I'll also add that a highly respected DeLorean guru recently told me he recommends and uses Castrol 15W40 DIESEL oil. I read through a few varying opinions on diesel oil usage on this forum, but this guy definitely knows what he's talking about. SO - I'm still concerned about my cams and can't decide which oil I'll use for my next oil change. My gut says go with "the guru." Question: has anyone used the Castrol Edge 5W-50?

From observational experience it seems if you have an older motor that used the older oils with high ZDDP content (zinc) the surfaces were "conditioned" and can survive on the newer oils with lower levels of ZDDP. If you still want to use an oil with higher levels of ZDDP, the oils marketed for diesels and high mileage motors still contains high levels of ZDDP (at least for now). I do not think it is wise to use additives since you don't know how much ZDDP is already in your oil and how much you are adding with the additives. Too much of a good thing is usually not good. Bottom line, using any good oil is probably OK. As I said in the last post, regular changes is more important than how much ZDDP is in it.

[82DMC12]

There are so many threads related to motor oil I wasn't sure which to use. Here goes: I've always used Castrol 20W-50 as that seemed to be the consensus of numerous long term owners. I'm told that Castrol used to publish the amount of zinc in their oil but then stopped doing so, leading many to believe that the zinc level has gone down below what is needed for our flat tappet cam engines. So I had some time today and I called Castrol. Here's what they said. They do NOT provide data on their oils because it's proprietary info. Furthermore, the ONLY oil they manufacture specifically for classic cars needing sufficient zinc is Castrol Edge 5W-50. That's it. The only one. And it's a full synthetic. I'll also add that a highly respected DeLorean guru recently told me he recommends and uses Castrol 15W40 DIESEL oil. I read through a few varying opinions on diesel oil usage on this forum, but this guy definitely knows what he's talking about. SO - I'm still concerned about my cams and can't decide which oil I'll use for my next oil change. My gut says go with "the guru." Question: has anyone used the Castrol Edge 5W-50?

I've used Mobil Delvac 1300 15w40 for over a decade. It's technically a diesel oil but excellent in older gas engines needing zinc/ZDDP. Do some research on it.... good stuff. Just had my valve covers off for the first time in maybe 12 years, they were 100% spotless with no sludge. I have to admit I only change the oil every year or two. Oil pressure is perfect too.

Andy