I am currently getting 21 miles per imperial gallon doing mixed driving. This is about 185 miles between filling up and hitting the red. At $5.50 per gallon I want every mile I can get. I am interested to know if this is about right for these cars.
The car was only bought a month ago and the stat was faulty (stuck open) with the temperature gague showing just above 100. I have changed the stat today and the needle is at about 190 deg. Do you think a cool running engine may effect fuel economy?
Thanks

Simon Holtby

'88 Camaro IROC 5.7 TPI

 

An Imperial gallon is slightly larger than a US gallon, so I would say your mileage is actually quite good. Canadians will be able to answer this better.

As for temperature affecting mileage, yes. If the engine is running too cool, the ignition and fuel mixture are increased, resulting in more power but lower gas mileage.

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FORMULA 350 TK
Southern California 3rd Generation F-Body Organization©

 

What's a gallon? We use litres here

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1984 Silver Z28, 383 cid 4 bolt, ARP Fasteners, 2 1/2" Cowl Induction Hood, 600 cfm Performer Carburetor, Torker II Intake, Performer RPM Heads, XE268H Cam, Magnum Roller Tip Rockers, MSD6AL Ignition, Blaster2 Coil, Recurved HEI Distributor, 700R4, TransGo SK, 2.73:1 Limited Slip Dana 44, Terminator Headers, Custom 3" TIG Welded Stainless Exhaust, Flowmaster Muffler, 4 Wheel Disc Brakes, Oil Cooler

 

Since you're using liters to fill the tank, convert liters to gallons.. 3.875 lts to 1 gal. Then recalc your milage,you'll find its likely to be nearer 25, unless you're driving up the M1 at 80 plus. Which, when I lived there was common.

 

Hmmmm......

Well, when I drove across Canada in 1974, I was buying Imperial Gallons.



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FORMULA 350 TK
Southern California 3rd Generation F-Body Organization©

 

Hey man, that was back in the day

 

Prices are all quoted in litres in the UK now but miles per litre means nothing to most people here. We have the EEC to thank for banning the use of imperial measurments people get fined if they do.
I think a US gallon is 20 % less than an imp. gallon.
Why did Canada go metric? Someone told me it was because they thought the US was planning to but then changed their minds.
Regards

Simon Holtby
'88 Camaro 5.7 TPI

 

I'm not sure what most people with TPI get for mileage, but 21 miles/Imperial gallon sounds a bit low to me. That's less than 17 miles/US gallon.

The open thermostat probably kept your ECM in open loop, which would lower your mileage. The proper operating temperature should help.

A good way to improve your gas mileage and help your car last longer is to convert to synthetic lubricants, especially engine, transmission, and differential.

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 2.73 open. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

Being an old fart and raised in Canada, I can remember the good old Imperial system (which was dropped in 1977).

1 Imp Gallon = 4.54 L
1 US Gallon = 3.87 L

I'll let you do all the math, but I get over 600 Kms (375 miles) to a tank on the open road. 400 kms (250 miles) in basically pure city and 450-500 kms (280-310 miles) in mixed driving. Definitely something is not right with your car.

BUT, it can also be fuel related. Alcohol does not have the same BTUs as pure gasoline. Many places are now adding Alcohol to the fuel to cut down on emissions (and reduce the Arab oil cost). Also, it is often added to gasoline during winter in many locations.

Right now, my fuel mileage has definitely dropped in the last month or two. My car was recently tuned and running very good. The only difference, is we now have a "winter blend" of gas and my mileage has dropped about 15%. This is consistent with previous years, and when I researched this a while back, I found out about "winter blends" of gasoline.

So if you car is in good tune, and this is a "recent event", it may very well be your gas.

 

Glenn91L98,

How the hell do you manage 280-310 MILES to a tank on a '91 GTA with the L98? WTF?!

I have a carbed LG4 that gets like 300KM (220 miles?) to a tank combined driving.

Actually, I do punish that poor vehicle.
Nevermind. =P

 

i have gotten on a road trip once as high as 28 mpg on my lg4.. thanks to the 2.73 rear end gears

Steve

 

Hype, the majority of the time I tend to drive the speed limit on the highway and I don't boot it much when I am in the city. When I drive the Coquahalla, I generally set the cruise control and do 105 Km/h (65 mph).

My mileage is based on a "two way" average of a trip from Kamloops to Abbotsford/Mission area and back. It is about 600 km both ways and I can do it on one tank of gas.

Above 105 Km/h (65 mph), I notice my gas mileage start to drop significantly.

 

i get between 21 and 26 mpU.S.Gal

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87GTA,350,Auto,MAF screens removed,195 thermostat,cold start injector UNPLUGED,K&N,modified air intake,ADSchip,3:70s,3inch cat back Flowmaster single outlet,TPS.54,Bosch Plat plugs,base timing 6BTDC,22 MPG and runs like a bear,Bilstiens in the rear....,don't let yer meat loaf

 

last year when I bought the car I was getting about 16mpg city 21mpg highway this was when the car was all stock and with 23000km (14000miles) on the car.

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89 GTA 350 5-speed
(Jet hot coated) SLP headers,flowmaster force 2,no cat's,SLP cold air,MSD 6al,jet chip stage 2,march pulleys,ported plenum,air foil,B&M ripper shifter,180 stat,alston SFC,spohn LCA relocation brackets,MAT relocation kit,free mods.

G-Tech times
0-60 5.3s
E.T. 13.91@104.8MPH (2300ft)

 

Glenn,

From one old Yankee fart to one old Maple Leaf, I recall when I was shopping the gas stations for 97 octane premium (leaded, of course) among the local gas wars for 26 cents per U.S. gallon. The attendants would even check the tires, oil, and wash the windows, since we couldn't pump the gas ourselves.

Not to start an international inceident, but you need to remember that only a part of the power produced in an engine is from BTUs of combustion. The majority of the pressure increase in the cylinder is created from the increase in the volume of gasses created in the combustion process. Combustion is a physical AND chemical process, and it changes the number of molecules of gasses of all varieties (mostly nitrogen and oxygen) into a lot bigger variety of gasses with individual, distinct molecules occupying the same space. In essence, one liter of a nitrogen/oxygen/gasoline vapor mixture will convert to a liter of sulfer dioxide, carbon dioxide, carbon monoxide, hydrogen sulfides, and will still have some leftover free nitrogen and oxygen. The total volume of gasses in the cylinder instantly (well, almost) increases to about four liters of variety gasses. It is this pressure more than the thermal expansion caused by the heating of gasses that causes power. Alcohol mixed into the gasoling helps in power generation by further increaseing the number of gasses produced.

You are correct in stating that alcohols burn with fewer BTUs produced than pure light hydrocarbons, but you hardly ever see top-fuel engine using gasoline instead of methanol blends to produce the maximum power output. BTUs aren't the whole story, or even the biggest part of it.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

vader
i knew you were the all knowin of this board and i have never seen a tough question not get answered correctly by YOU, but why did i picture you as some 23 year old punk kid like myself...well im only 19 but still. oh and why Vader(as your nickname)?
oh and i dont know maybe my car just sucks gas like a vampire does blood but i get about 130 miles per tank. maybe about 10 miles per gallon. but i get from L.A. to S.F. on one tank. just under 400 miles. clean air filter, new spark plugs, msd wires. whats the deal. gas it like 2.00 a gallon up here. help. 305TBI 90RS

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Rick
90 Camaro RS 305 TBI
350 on the way!!

 

Hi Simon

Nice to see another UK member on this board !
I'm down in Surrey, near Gatwick airport. This morning due to the heavy rain, there is loads of flooding. How has the weather affected you ?

Anyway I have an 89 firebird (305 TBI) and I get between 15-18 mpg (imperial). I mostly do town driving and travelling to and from work only takes approx 5 mins. On the odd occasion that I've done some motorway driving then my mpg goes up to 20/21 mpg.

If anybody knows how to improve my mpg, please let me know, by the way, I'm not heavy footed either.

Geoff

 

Vader, very true that engines "designed" to run alcohol (ie. very high compression) exceed gasoline engines. The problem is, 9.5:1 is not optimum for alcohol.

Where I live, virtually all the gas stations add alcohol (of some sort) to their fuel during the winter. This was addressed by the oil companies here when people started asking "why is my gas mileage poorer in winter" and the above was their explanation.

Today, I think virtually all gas stations add some alcohol to their gas all year-round, just for emission reasons. Given that, may be "we" should start bumping up our compression a little more than 9.5, to take advantage of the alcohol in the gasoline today.