94corvetteC4

Just checked my first tank of gas and got a disappointing 17.1 mpg from that tank. This is all city driving and took me 3 weeks to go from a full tank to reserve. I don't drive the car hard and I noticed my rpm's are usually around 1500 when cruising between lights. I was expecting something closer to the low 20's or 20 mpg at worst.


The air filter is new and their are no error codes so everything should be working. Wondering if new O2 sensors would be in order. I know that as they get old they slow down and that negatively effects gas mileage. My car has 102K and they could be the original O2 sensors.


I usually install a K&N air filter in all my cars and always notice an improvement in mpg after doing so. The filter in there now is a regular paper air filter.


Going to do Sea Foam through the vacuum line and gas tank just for ***** and giggles since I don't know how well the previous owner took care of the car. I have never done this before and always wanted to see if it helps any so now is a good time to try it. Then maybe a new fuel filter and K&N air filter.


Any other ideas on how to get the mpg up or is 17 normal for a 1994 C4 LT1 6 speed?

toricred

I've got a 1996 CE LT1 Auto and I'd kill to get 17mpg. I'm usually around 13-14mpg in town. I'm rarely out of town so I don't see much better anytime.

trilkb

Considering the factory sticker claims 17 city and 27 highway I would call that about right haha. Basically its not a number that would make me question if my car was healthy or not.

13-14 seems pretty low, but depends on your driving. If your very easy on the car I would try changing a fuel filter and air filter, pcv valve. I had one lt1 that ate gas like a champ when I bought it, turned out the fuel pressure regulator didnt have its vac hose attached. If I got 13-14 driving how I drive I would be looking for the cause for sure.

kdf1986

Hello
I have an 86 automatic. 16-18 mpg for city driving is about what I get. And around 22 on the highway.

kdf

Onlyone

I have a mix but mostly just driving to work and back about 8 miles each way. Half of that is city, the other half 55 mph hwy. it's always at 25 mpg. I'm also at 7000 ft too.

94corvetteC4

I did a Google search for 1994 corvette specs and it appears I am right in the MPG range listed by GM. Considering I have 102K on the car I'm doing well. Had I thought about doing that search earlier I wouldn't have started this thread.

Hopefully some owners who have been able to get their gas mileage up will post what they did so that the rest of us can benifit from their ideas. I'm going to leave the O2 sensors in the car but I will do the Sea Foam trick, replace fuel filter and add the K&N air filter to see what happens.

antfarmer2

You should be your third set of 02's
It is much easyer to pull the filter out the top

gerardvg

Man

I wish I got 17 mpg on the highway

I recently bypassed the blower, putting it back to standard for Summer here in OZ. and I swear I get worse mpg in standard form.

I know the dash may display 20+ mpg but it lies ........

Cliff Harris

I get about 15.1 MPG (dash reading) around town with 3.07 rear gears.

The best I ever got was 22 MPG going to Phoenix during the summer with the A/C on.

hcbph

I have an 86 with a Tremec 5 speed. My initial mileage readings I found were off because the speedometer was running fast. Since correcting that, I have been getting around 20 mpg around town and 26-29 mpg highway. I drive it easy so no stoplight blasts, just normal acceleration between lights.

Had previously a best of 32 mpg highway but then I found the speedometer (and odometer) were running 10% fast.

jph46

When you pull the Fue line up to change the filter do both lines (feed and return) need to be pulled or just the feed line?
Thanks

bob arrowsmith

When I first got my car I was getting between 17 / 25 with 2.59 rear end ,,had all u joints rear hub replaced and while there went to 3.07 s, installed the hypertech program and am getting 16/22 now so depending on your right foot results may differ.

Joe C

90 automatic - standard gearing - 14 city, 23 highway, and overall average, upper 18 (dash board indicated). best I ever got with a C4 was my 96 LT1 (auto of course), standard gearing - 28 highway (99% highway, easy driving, and old school math). all three of my L98 cars were about the same - 14/23 and shy of 19 average. bottom line - when I need gas, I stop and get gas -

in any event, much better than my C3!

mike100

You are disappointed with 17 mpg combined from a car with a 350 V8?

Actually this is a very good number and about what I got on mine as well as what I have achieved on my 5 liter pony cars over the years including my 2012 mustang GT.
Better mpg can be had from C5 and C6's because of the drivetrain efficiencies using a rear transaxle. Also gasoline btu content is down with alcohol blending- I just don't see how you would expect to get 19-20 tooling around locally.

antfarmer2

both lines the connection for the return line is right by the filter.

while your under there pull your knock sensors and give it a proper flush.

Richard Raichert

It was 17 city highway 24. Not so sure about getting 17 in the city unless you don't have the a/c on which is rare in FL. I have got 30 mpg on the highway, no a/c on and all interstate but that was going downhill from north GA to FL!! (once)

whalepirot

I run tire pressure close to max sidewall (proper wheel alignment, too), depending on tread wear patterns. Some consider this a part of hypermiling.

Driving a Smart Cabriolet taught me:1) economy is inversely related to RPM, getting 27 or 42; all in the footwork, and 2) smooth driving,(sounds like you know that) meaning maximum interval between throttle and brake pedals.

OR only drive downhill!

bob arrowsmith

Wale is right , also when the tester for any automobile sets there initial mpg factoid there testing is like the little o lady from Pasadena not like us who occasionally will test the limits do that a couple of times on a full tank and see what happens,,it is what it is , if your car is in tune. enjoy your ride and drive safe...

Mr. Peabody

Your 17mpg is right on target. On the highway the stick will do much better in gas mileage than the auto but I think that around town one is not going to be significantly better than the other.

Please do not make a habit of letting the gas level in the tank go down to the point where you are on reserve. The fuel pump motor is in the tank and is cooled by the fuel.

Lots of folks like the K&N filter but I had a bad experience the only time I put one in my 95 due to excess oil on the filter out of the box. I've gone back to the paper filter and just change it out each spring.

94corvetteC4

Yes I expected better even from a 350cid.


My 2007 Mustang 4.6 5speed mildly built 365whp 331pft with 373 gear gets 18-20 city driving and I drive it harder than the vette.


My 87 Grand National that ran only the stock block with all HP parts, level 10 200r4 trans non lockup and 342 gear was getting low 20's with the boost set at 15lbs and 36lps fuel pressure on the 42.5 fuel injectors. This was a combination of highway/city driving in a car with 532rwp. When I turned up the boost and the fuel pressure and ran that car the way it was built to be run it sucked down some fuel!!!


1997 Chevy Z71 350 vortec, K&N air filter, 4l80e trans, 342 gears and BFGoodrich All Terrain T/A tires was getting 17-19 mpg city. Best MPG was 23 on a trip from Atlanta to Illinois with Michelin tires. I filled the tank, got on the interstate, set the cruise at 65mph and drove till it was almost empty to get to 23MPG.


If I can get 17-19 out of a 4 wheel drive truck with a 350 auto and mud tires I should get that out of a much lighter car with a 6 speed manual trans and much more advanced engine. At least in theory.


I know that some vehicles just don't get very good gas mileage. I have a few friends with Ford trucks with the 302cid engines they tell me the ford trucks have no power and get very bad gas mileage.