Mpg

[jfirios]

I am still even after all the mods to the engine and upgrades I am still getting about 12-15 MPG. I am using 91 octane too. I don't really have that much of a lead foot maybe 50% lead :) But still that shouldn't account for that poor gas mileage. I went from my place to DMC Cali which is 50 miles from my house and went through just over a quarter of a tank. It is tough to fully gadge it since the needle floats so much, but I had it full when I left. I don't know what else can fix the problem. Could it be the Lambada sensor needs replacing or the Lambada control itself? What do you all think?

[DMC5180]

HMM, Los Angeles. Don't you mean 12-15 MPH and 5 hours to make the trip.:biggrin:

[jfirios]

Aint that the truth. I have never lived in a place before where I had to factor in an extra hour of drive time no matter where I was going, either down the street or to the airport. Honestly, If I wasn't making movies for a living, there is no reason to live here.

[WelmoedJ]

Doing calculations based on miles (trip counter) and the fuel gauge will not give you the most accurate result.

For a start: fill the tank until the nozzle shuts off, note the mileage on the odometer and reset the trip counter. Save the gas receipt.

Do so each time you fill the tank (same way of filling makes calculations more accurately).

Over time you will have figures on mileage, gallons and cost.
Use a spreadsheet to note all your figures and use formulas to calculate what your car actually used between each refill (gallons) and what your mileage is for the distance in between the two visits to the gas station.

I have this working for both of my cars since their purchase.
Should you want to use my spreadsheet file, PM me.

[Bitsyncmaster]

City driving is so dependent on the driver and conditions, I never bother checking the MPG unless I'm on a long trip.

With all the idle work I do perfecting my ECU software, I'm lucky to show better the 10 MPG.

[stevedmc]

I get between 17 and 28 mpg driving my manual transmission D with a carburetor on the back. It just depends on how I drive. Most of the time I get 25mpg.

Now for the important information. You cannot accurately calculate your gas mileage if your speedometer is off. When my speedometer displays 65 mph I am really driving 75 ish. I did some basic algebra (I used slope) to determine what to multiply my odometer reading by to get real miles. You can figure this out by comparing one mile on your odometer to one mile on the interstate (use mile markers). Then do a little algebra and you know what the difference is. I did this to figure out I need to multiply what my odometer says by 1.127 to get the correct mileage.


Lets say my trip meter reads 100 miles and it takes 5 gallons of gas to fill up. Here is the math I do:

100 miles x 1.127= 112.7 actual miles
112.7 actual miles / 5 gallons = 22.54 mpg

[nofear365]

just wondering, why 91 octane?

[thirdmanj]

I get between 17 and 28 mpg driving my manual transmission D with a carburetor on the back. It just depends on how I drive. Most of the time I get 25mpg.

Now for the important information. You cannot accurately calculate your gas mileage if your speedometer is off. When my speedometer displays 65 mph I am really driving 75 ish. I did some basic algebra (I used slope) to determine what to multiply my odometer reading by to get real miles. You can figure this out by comparing one mile on your odometer to one mile on the interstate (use mile markers). Then do a little algebra and you know what the difference is. I did this to figure out I need to multiply what my odometer says by 1.127 to get the correct mileage.


Lets say my trip meter reads 100 miles and it takes 5 gallons of gas to fill up. Here is the math I do:

100 miles x 1.127= 112.7 actual miles
112.7 actual miles / 5 gallons = 22.54 mpg

And here I thought you didn't have a brain.... That seems pretty brainy, have you been holding out on us Steve?

[sean]

And here I thought you didn't have a brain.... That seems pretty brainy, have you been holding out on us Steve?

Steve's a brain sandbagger.

[stevedmc]

And here I thought you didn't have a brain.... That seems pretty brainy, have you been holding out on us Steve?

Honeybadger don't care.


just wondering, why 91 octane?

The only reason to run a higher octane gas is if your engine is having problems. 16510's original engine had low compression and a blown head gasket. This resulted in a knocking noise upon acceleration. I was able to "cure" my knocking noises by switching from 87 octane to 89/91 until I was able to replace the enigne.

[nofear365]

Exactly. A PRV that is tuned correctly runs fine off 87 octane all day.

[jfirios]

I was just trying out different octanes to see if I would get better mileage. My spedo is just about balls on with my gps.

[Ryan King]

I am running a Stage II automatic and I'm getting, at best, 18 MPG

[stevedmc]

I am running a Stage II automatic and I'm getting, at best, 18 MPG

Something has got to be wrong. Are you sure your odometer is accurate when you calculate mpg? I think Chad is getting slightly more than 30 mpg on his stage 2 engine.

[Ryan King]

Something has got to be wrong. Are you sure your odometer is accurate when you calculate mpg? I think Chad is getting slightly more than 30 mpg on his stage 2 engine.

As far as I know its accurate..I dont know what could be causing me such horrible gas mileage

[nofear365]

Assuming the engine is properly tuned, proper octane will not give you increased or decreased performance & fuel economy.

[Rad Dad]

My '83, manual with twin turbos, gives 24/25 on the highway at speed limit +5. My first DeLorean was an automatic, also with twin turbos, and it was 1.5/2 mpg less. I normally only check mileage on trips, but around town, I'd guesstimate I get 15/17 depending upon driving style. And, yes, I use premium because of the turbos.

[Chris4099]

Now for the important information. You cannot accurately calculate your gas mileage if your speedometer is off. When my speedometer displays 65 mph I am really driving 75 ish. I did some basic algebra (I used slope) to determine what to multiply my odometer reading by to get real miles. You can figure this out by comparing one mile on your odometer to one mile on the interstate (use mile markers). Then do a little algebra and you know what the difference is. I did this to figure out I need to multiply what my odometer says by 1.127 to get the correct mileage.

That may be giving you inflated MPG numbers. The odometer is directly geared off the speedo cable while the speedometer is driven by magnets. It could be your speedometer is just out of adjustment which would give you lower readings while your odometer is dead on (not adjustable). You should really verify the odometer against mile markers or a GPS.

I also agree that you should never try to calculate MPG based on the fuel level sender. Mine drops by a 1/4 of a tank after just 20 miles and spends nearly 100 miles hovering around the half tank mark. Fortunately my phone has a mileage app that allows me to easily keep track of my MPG with every fill-up.

[stevedmc]

That may be giving you inflated MPG numbers.

Nonsense.




The odometer is directly geared off the speedo cable while the speedometer is driven by magnets. It could be your speedometer is just out of adjustment which would give you lower readings while your odometer is dead on (not adjustable). You should really verify the odometer against mile markers or a GPS.

I have compared my odometer against mile markers. I had to in order to make my calculations using slope. You must have missed what I said about that. I've also compared my speedometer to a GPS speedometer. Both the speedometer and odometer are equally wrong and must be multiplied by 1.127 to get the correct number.

I might not have a brain but I was pretty dang good in algebra back in my college days.




I also agree that you should never try to calculate MPG based on the fuel level sender.

How on earth is it even possible to calculate MPG based on the fuel level? Am I missing something? I always thought the only accurate way to calculate MPG was to fill up the tank.

[Chris4099]

Your right, I missed that sentence where you said you used mile markers. That made me think you were calculating distance based on the speedometer inaccuracy. As for the last part, that was directed to the OP who said he went 50 miles on a quarter tank.

[stevedmc]

Your right

Amen.

[jfirios]

Still though, assuming that I am getting say 15MPG and the engine is working properly, is there any way to increase the MPG?

[DMCMW Dave]

Still though, assuming that I am getting say 15MPG and the engine is working properly, is there any way to increase the MPG?

If you are getting 15 mpg the engine is, by definition, not working properly. Unless:

--You drive only in city traffic and rarely get above 30 mph and not often past third gear (this could happen in LA!);

--You drive an automatic with a bad computer governor that never hits third gear;

--You have an extremely heavy right foot or seriously sticky brakes.

A properly tuned DMC will get 18 city (17 automatic) and 28 highway (25 automatic) without trying very hard. On an extended road trip at 60 mph you can easily hit 30 mpg with a manual. Stage 2 makes no difference. I've had some report that it's better after Stage 2 but I attribute that to the fact that the car was probably out of tune before the upgrade (Stage 2 includes all the ignition tuneups and a set of injectors).

I suspect Stage 3 will be a whole different story though. . . .:smile:

[Bitsyncmaster]

If your basing your 15 MPG on that one 50 mile trip and the gas gage moving a 1/4 tank your accuracy on that reading is probably 50%. So your probably getting 7.5 to 22.5 MPG.


Fill up the tank and record the miles on the odometer. Then next time you fill up, record the gallons it takes and the miles on the odometer. Report those values back here.:bigclap:

[SoCalDMC12]

Stop-n-go traffic has become the norm here in LA, so lower mpg's seems somewhat expected. But I don't think I've gotten down to 15 mpg on a tank (stage 1, 5-speed, ~131k miles). Are your tires inflated properly? Air filter clean? I've read that basics stuff like this can increase economy a bit.

[Rich]

Two more possible culprits re bad fuel economy in this or other cars with previous owners and suspicious maintenance history.

1. Check your brakes. A sticking brake caliper/piston will drag the fuel economy down - you may notice no other symptoms of it possibly aside from excessive brake dust on the affected wheel(s) or maybe seeing that the car does not coast so well at low speed in neutral. Each wheel should rotate freely a few turns when spun. Infrequent brake fluid renewal can cause a frozen-stuck caliper.

2. Be sure the thermostat is there and is operational, especially now in cooler L.A. weather. Engine efficiency drops dramatically when not at proper operating temp. Dash gauge is a start - a mechanic can check it with an IR thermometer as well.

[stevedmc]

I would check ignition first and make sure all spark plugs are firing. Make sure they are properly gapped too.

If your spark plugs, wires, rotor, ignition cap, and coil have never been replaced, now might be a good time to do so. Regardless though, I'd check to see if the plugs are firing.

[jfirios]

so far i have replaced almost everything in the car. Since i got it in july, i have put on the break upgrade kit, the relay upgrade kit, the stage 1 upgrade, the hose upgrade kit, the ignition upgrade kit, the fuel pump kit, all new injectors, all new plugs, all new seals in the intake manifold, the shocks and springs upgrade kit. Don at DMC said she was running really well, and it passed smog, but who knows. That is why I am asking what I should be getting. Next is the fuel sender upgrade, and am thinking of installing a CAI instead of the air filter system we have on now.

[DMCMW Dave]

If it passed the California smog test it's probably running fine. That's very unforgiving of things like bad plugs and wires.

Is it a manual or automatic? What is your usual driving environment and/or style?

[stevedmc]

15 mpg is very doable under extreme circumstances. I managed to drop my gas mileage down to 17 mpg once by driving like a crazy teenager in city traffic. I only drove crazy like that once and have never seen gas mileage that low since then. Usually my low is 22mpg and my high is 25. Although I can get 28 if I drive like an old man.

[jfirios]

my driving habbits are normal i guess, no heavy racing, highway is about 70-80 normally, unless stopped in traffic burning out first gear going 3 miles an hour.

[tgraham]

I finally calculated my MPG for the past couple of fill-ups after rebuilding my engine and putting ~1500 miles on it. The current average: 17.85 miles/gallon.

A few notes, though:

1) This average is for ~60% city driving and non-ethanol fuel
2) The engine is no longer stock (different cams, head work, and exhaust)
3) I've been suffering from an extreme case of "lead foot syndrome" since getting this car back on the road. This problem manifests itself both in acceleration off the line and speeds on the freeway...

#3 is the big red flag, but I'm simply having way too much fun driving the car!

Travis

[Jeff K]

My stage 2 auto gets about 18-20 in town, about 25 on the highway. It was recently tuned up by DMCCA and it passed smog easily.

I can't accept people are getting 30mpg - the way they are measuring is incorrect IMHO.

I use a GPS tracker program to calculate distance traveled and I found the speedo is off about 10-15%. 85% of 30 is 25.

Again.. that's my 2 cents..

[dmc6960]

I can't accept people are getting 30mpg - the way they are measuring is incorrect IMHO.

30mpg completely doable with a well tuned engine on a single continuous run of 60-65mph of level highway with no headwind.

I got 31 mpg on one fillup on the way to DCS'10, including a witness. 28-29 on most others.

On my very first cross country drive with the car back in 2001, bone stock engine, I got an average of 27mpg over the whole 3200 mile trip. Many fillups at 28 and 29mpg.

I have a 5-speed.

[Jeff K]

30mpg completely doable with a well tuned engine on a single continuous run of 60-65mph of level highway with no headwind.

I got 31 mpg on one fillup on the way to DCS'10, including a witness. 28-29 on most others.

On my very first cross country drive with the car back in 2001, bone stock engine, I got an average of 27mpg over the whole 3200 mile trip. Many fillups at 28 and 29mpg.

I have a 5-speed.

That's great! Was that before or after you car was EFI?

[stevedmc]

I can't accept people are getting 30mpg - the way they are measuring is incorrect IMHO.

Nonsense!

I can get 28mpg whenever I want to with my carburetor. All I have to do is put real gas in the tank and drive like an old man on the highway.

If I were to do some hypermiling I could get way over 30 mpg but I've chosen not to do that in the Delorean. I reserve hypermiling for my Geo Metro. I normally get 50 mpg in the Metro but with extreme hypermiling I've hit has high as 67 mpg.

[Jeff K]

Nonsense!

I can get 28mpg whenever I want to with my carburetor. All I have to do is put real gas in the tank and drive like an old man on the highway.

If I were to do some hypermiling I could get way over 30 mpg but I've chosen not to do that in the Delorean. I reserve hypermiling for my Geo Metro. I normally get 50 mpg in the Metro but with extreme hypermiling I've hit has high as 67 mpg.

Hey, great to hear. How are you measuring it?

[stevedmc]

Hey, great to hear. How are you measuring it?

With math. See posts #6 and #19.

[Jeff K]

With math. See posts #6 and #19.

Nice, I would never have figured math plays a part. Amazing what this board teaches us.

I still think a GPS tracker is the only real way to be accurate. But I really don't care.

[bkntym]

My MPG improved huge with two things i did.

1. Took apart right front caliper unjammed it and instantly gained 5mpg.

2. I did the lean out trick. it smelt rich when idleing, now it smells good, like a two stroke dirt bike when your nine years old. ya it smells good. and it gained another 5pmg.

i used to get about 120 miles on a tank. now well over 200 miles or 320 km for us Canadians.:jawdrop:

[dmc6960]

That's great! Was that before or after you car was EFI?

The 31mpg on the way to DCS '10 was EFI, with the new-ly rebuilt engine (Rebuilt in 2009, high compression [10.8:1], headwork, exhaust). Set slightly lean at a highway cruise (~15.0-15.2afr).

Immediately after the engine rebuild, but before the EFI, I got 27mpg highway.

The 27-29mpg back in 2001 was a bone stock K-Jet engine.

[stevedmc]

Nice, I would never have figured math plays a part. Amazing what this board teaches us.

I still think a GPS tracker is the only real way to be accurate. But I really don't care.

Gps trackers aren't always accurate either. If you look at a GPS trail closely you will notice zig zags in places where you turned. I never drive in zig zags.

[dmc6960]

Also to throw this out there, my 31mpg reading was on the slowest travel segment of my drive. Kept mostly at the speed limit of 65mph, occasionally driving to 68-70mph. Most other segments were at 70mph minimum.

There is a reason the government set the national speed limit to 55mph back in the gas-crunched 70's. I could probably get 35mpg if I kept to 55-60mph.

[stevedmc]

There is a reason the government set the national speed limit to 55mph back in the gas-crunched 70's. I could probably get 35mpg if I kept to 55-60mph.

I've been saying for the last 4 years the speed limit needs to be dropped to 55 mph on the interstate. It would turn gas guzzlers into fuel efficient cars overnight.

And a lower speed limit would instantly generate more revenue for the governemnt (more speeding tickets). Its a win/win for everybody, except for people who refuse to slow down.

[Farrar]

My daily driver seems to be most fuel efficient between, generally, 45 MPH and 60 MPH. I have yet to test the D's fuel efficiency (been plagued with vacuum leaks since day one), but I imagine it's roughly the same -- rumour has it that the government's fuel efficiency test is done at 50 MPH.

Farrar

[awildermode]

I was getting about 12 mpg. Then I had a major tune up, now I am getting an awesome 14 mpg. This is mostly city driving. I can get about 17-19 on the highway.

[jawn101]

I usually get about 21 MPG combined mileage, but that's generally with at least 30-60 miles done on the highway at around 70. Respectable enough.