87 or 91 Non-Ethanol?

[DMC-81]

The bad batch comment above is in my opinion rare but does happen.

Yeah, it's not typically the quality control of the refining process, but how it is stored. My brother also worked at gas stations at the start of his working career and through that experience, said never fill up when you see the tanker truck there. Reason being, when new gas is pumped/drained into the underground tank, this action causes anything at the bottom of the tank to be kicked up (water is the main concern here) and in turn pumped into your car. There are variables of course.. the condition of the tank, age, turnover of the gas, weather, etc.

Nick's (OP) symptoms almost sound like water in the gas. Who knows? If so, you can get an additive to remove the water from the tank.

You would be able to tell right away if it was 20 below zero, as the fuel line would freeze. I've had that happen....not in Florida of course.

[AugustneverEnds]

Lots of discussion, I like!!

I know this is a stretch but I was thinking even though the engine runs 8.8:1 compression and should be fine with 87 maybe it has grown used to 91 after a steady diet of it for the past 16 years or so. The previous owner (2002-2012) I bought the car from explicitly told me he always and only filled up with 91 ethanol free and I have done the same since August 2012. Maybe my silver beauty is telling me it hates the hamburger I tried to feed it and wants the steak again

It was warm and dry here this afternoon and the short drive home was drama free.

[DMC5180]

24 years and about 65000 miles on 87 Regular (ethanol blend) ZERO fuel Related issues. Spark issues, yes. Due to component age. The engine was certified to run on 91 RON (Euro standard) which is the Equivalent to our 87 using the (R+M)/2 method.

Unless you have a Stage 2 engine, running 91-93 premium will just lighten your wallet quicker. If you think your car runs better with it, it is likely because you have other issues going on in which the high Octane is masking the problem. Such as carbon build up in the combustion chamber and pistons tops. This is why it is suggested to bump up to Mid-grade octane once an engine gets into the 100k territory. The slightly higher octane helps compensate for the typical age related issues of older engines.


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[Ron]

Also the number at the pump is not exactly a octane level as much as it is a anti knock rating.

Yeah, actually it's not a 'level' at all...Overseas, it is a rating/measure of anti-knock characteristics, exactly. They use a standard called Research Octane Number (RON). Here, they use RON and another method called Motor Octane Number (MON), averaged together. Sometimes it is called PON (Pump Octane Number). Pumps may say PON, RON+MON/2, or R+M/2. RON determines characteristics during low speed and load. MON for high temp, speed, and load.

(Cliffsnotes Version ;-)

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+1 on high octane not improving anything, with lower compression engines -- A waste of money. I guess people think "Oxygen", or something...or jump in because high power (high compression) engines require it?? It helps prevent knock because it is harder to ignite and burns slower. That doesn't sound like more power to me...
(But, being able to squish more of it does... ;-)

[David T]

One thing I did notice is that you get slightly better gas mileage on the higher octane fuel. Not enough to justify the difference in price. Do NOT compare how a Delorean can run on different octane fuel to a modern car with Engine Management. Modern cars will modulate the timing to prevent engine knock when using lower octane fuel but it will decrease performance. Best if you can use non-ethanol fuel but here in New Jersey you can only get E-10. If you use the car regularly and don't store the car with fuel in it, E-10 will work but it does eat up the rubber parts in the fuel system like the boot and cover for the fuel pump. Do NOT add anything to E-10 for water. What you are adding IS ethanol aka "dry gas". Adding more Ethanol will just make things worse. If you have E-10 and you are having issues with water you must drain it all out. Deloreans were made to run on 87 octane fuel but not E-10. If you have modified the motor or have a Stage II and you hear knocking you must increase the octane you use or retard the spark.

Note: E-10 is fuel with 10% Ethanol and no lead.

[nullset]

Lots of discussion, I like!!

I know this is a stretch but I was thinking even though the engine runs 8.8:1 compression and should be fine with 87 maybe it has grown used to 91 after a steady diet of it for the past 16 years or so. The previous owner (2002-2012) I bought the car from explicitly told me he always and only filled up with 91 ethanol free and I have done the same since August 2012. Maybe my silver beauty is telling me it hates the hamburger I tried to feed it and wants the steak again

It was warm and dry here this afternoon and the short drive home was drama free.

Your stock engine literally can't tell the difference between 87 and 91. 91 isn't "better" unless your engine is better - and your engine isn't.

Any difference you observe is almost definitely in your mind. Have someone else pump the gas a few times and see if you can tell the difference!

[Jonathan]

Your stock engine literally can't tell the difference between 87 and 91. 91 isn't "better" unless your engine is better - and your engine isn't.

Any difference you observe is almost definitely in your mind. Have someone else pump the gas a few times and see if you can tell the difference!

I sat in a sales/marketing meeting one day and the guy up front was talking batteries. Like which brand does everyone use. "Who here uses the good batteries?" And he gets a show of hands. "And why do you use those better brands?" ...because they last longer as the group all chimes in. Well, how long do they last? And no one can tell you because no one puts a sticker on their TV remote for the day they swapped the battery out and then again and again and again everytime you change batteries so you have some kind of data you can judge for yourself. Nope, you just use them because the commercial you saw on TV showed an old guy walking slowly in a hospital hallway and the caption was something about how you wouldn't want to trust your pacemaker with the cheap batteries, so you gotta get the good ones. But you don't know for yourself really, you just go with what everyone else told you was better.

Better ain't always better. Put 87 in your car.

[kbrown84]

I run 93 ethanol blend in my Stage 2...no issues yet, but I do wish I could get a non-ethanol fuel locally.

[DMC-81]

One thing I did notice is that you get slightly better gas mileage on the higher octane fuel.

I found that too, and probably has more to do with the actual ethanol content than octane. I’m sure that this varies by state, grade, and brand of fuel. Here is an explanation on worse fuel mileage with ethanol from Wikipedia:

“1.5 gallons of ethanol has the same energy content as 1.0 gallon of gasoline. A flex-fuel vehicle will experience about 76% of the fuel mileage MPG when using E85 (85% ethanol) products as compared to 100% gasoline. ... Pure ethanol provides 2/3 of the heat value available in pure gasoline.

https://en.m.wikipedia.org/wiki/Gaso...lon_equivalent

So, non-ethanol fuel in theory provides optimal mileage.

Do NOT add anything to E-10 for water. What you are adding IS ethanol aka "dry gas". Adding more Ethanol will just make things worse.

I’m not sure if the additive that I was referring to contains ethanol. Here is the content composition and link to the safety data sheet of the STP product that was a go to product for me when I lived in the Northern climes:

Attachment 56353
http://www.stp.com/sites/default/fil...2015-06%29.pdf

It mostly contains hydrosulfurized kerosene.

I think this is only needed if the problem was accurately diagnosed and persists after a couple tankfuls.

[AugustneverEnds]

Well warm dry morning here and the stumble was there at full open throttle and disappeared once the engine was warmed to operating temperature. Think I'm going to have to check the dwell and duty cycles and see if I have a problem with fuel enrichment.

Fill up with whatever fuel your heart desires!