I typically get an average reading of like 14.5mpg or so on my fuel guage. Granted I do have lots of neighborhood driving. But at same time under similar driving conditions my c5 gets between 18.5-19mpg and my other heavier BMW 740il gets like 15 to 17. Is this normal and should i do anything to fix this? I've heard maybe the MAPS should be looked at? I always use 93 exxon and usually add some stp gas treatment every other tank as well as techron before and after every oil change so id assume the fuel system is clean. Plus oil is always changed with mobile one full synthetic well before the 3k mile mark as well as the filter.

 

So when you do the math at fill up are you actually getting 14.5 mpg?

 

yes give or take a few 10ths of a gallon it is pretty accurate

 

I check at fill ups and don't really pay attention to the "average" on the gauge and my last three top offs have been between 19-21mpg.

 

Doesnt sound abnormal for lots of stop and go

 

EPA website says for my 85 auto 15 city, 21 highway and 17 combined. Window sticker says 16 city, 22 highway doesn't give combined. Right now the indicator says 20.3 and that is correct and typical for it. Most of my driving is 45 mph and above. Just search "epa mileage your year corvette" and compare it with that is the best advice I can give. If 14.5 is substantially lower than what should be expected then we can trouble shoot.

HTH,

Joe K

 

Cold starts (open loop) use lots of fuel. So if you're doing short trips and / or not letting the engine get to full temp, and / or not taking it on the highway very often, that could explain your situation. I'm not sure if the computer is able to compensate for open loop vs closed loop fuel consumption.

 

When my 86 was getting horrible mileage I found it to be a crack at the O2 sensor bung.
Have you changed the O2 sensor within the last two years?

 

I didn't buy my '96 (a few yrs ago) to achieve decent gas mileage. All I care about is how it performs and looks. However, a drastic drop in MPG would indicate an issue

 

You want high gas mileage? Sell your corvette and buy a Prius. Jus sayin'.

 

This might sound silly but when the Oxygen sensor fails it causes the fuel to be rich so you don't hurt the engine. The oxygen sensor is designed for a 24 months or 50k miles. If your car mileage has gone down and you have an older than 2 year oxygen sensor then try replacing the sensor/s. The signal gets narrower as the device ages, instead of oscillating between .1 and .9 Vdc it will oscillate between maybe .3 and .7 and the narrower signal is not able to get to the ECM fast enough so your O2 signal is lagging which hurts the economy and the performance of a Corvette. Anything with OBD2 will use 2-4 oxygen sensors and they last 48 months or 100k miles.

When your knock sensor fails the ignition pulls timing to protect the engine. My Corvette had lost power and the problem it turned out was the knock sensor was totally dead so the computer pulled back the timing.

Get a Bottle of B&G 44K Fuel System Cleaner, this stuff will remove any junk in the fuel system and clean the injectors as well. (It is used by hundreds of New Car dealerships every day.) the B&G 44K is the first thing I do when my car or Corvette starts missing a bit. The last time I used it the problem was gone within 25 miles of driving. It is available on Amazon or at local gas stations. I pay about $22 for a bottle today in Northern Virginia.

I probably get called out again for suggesting a "Snake Oil" as B&G 44K is affectionately called by a few online Forum members. I would not suggest it's usage IF I didn't use it myself, often. I stand behind the product's I suggest!

 

Yup V8 baby

 

Test the cat.
pull the o2 sensor out and put a pressure gauge in it’s place.
2-3 psi is normal.
5, you got a problem with flow.
take it 2 your fav muffler shop if u think u have a problem, and they can confirm it pretty quick.
cats can be expensive.
but now you could be at a point to upgrade your exhaust.
i have true duals with bullet cats on my 86.

 

I don't understand the comments about gas mileage and buying a Prius.

I want performance, AND I want fuel mileage. The C4 is a great platform for both.

I have an LT4 that has run in the high 12's and still gets about 30 mpg on the highway cruise. On another car I bought a '94 6M for my daily driver because it was a fun car to commute in and it got good mileage for my 100 mile per day commute to work. It was better mileage than my 4 cylinder 5 speed S10.

Once again, just because someone wants an all around car with both performance and mileage is no reason to imply that they should get rid of a great car to get something like a Prius.

 

What year is your C4??? You may be overdoing it adding STP gas treatment every other tank. Remember, your C4 is a 25+ yr old V8. Be glad it's running well and smoothly.

 

Agreed. If the OP said, "I don't understand why my C4 isn't getting 45 MPG" then the Prius comments would be relevant. Too many people think good performance and decent fuel economy are mutually exclusive. All Corvettes since 1984 have shined in that way -- they can give the best of both worlds, depending how you drive LOL.

For sure! My 1995 C4 gets the same average fuel economy as my 2006 Tacoma 4-cylinder, which is about 22-23 MPG, and they both run great. FWIW, my 1967 Mustang 6-cylinder did about the same (22 MPG).

 

Ill take teens for mpg if its a fun ride....in a rental ie '18 Altima. Mpg is off the chart but what a boring gutless pos. Lifes too short!

 

You guys crack me up. Surly a joke doesn’t always need to end in LOL. I get that if your MPG changes then it should be investigated because it’s an indicator of something being off normal. Sure with EFI engines you can get pretty good economy provided you are sparing on the loud peddle. My 6.0l LS powered 2009 SS gets 29 mpg on the highway allegedly but I’ve never got that. Normal driving around town gets 14 mpg and driving it the way it was meant to be driven yields a whopping 6 mpg.
Generally my 84 corvette does better but it doesn’t have anywhere near the power. Energy in equals energy out minus loses. So if you want to use power you need to burn fuel.
Im still with@Buccaneer if your overly concerned about fuel economy (and I’m not say the OP is) then a corvette is not for you. Maybe a Chevy Volt is your next car. (Do I need to add the LOL or do you get it).

 

17-19 on avg around town 24-28 on the big road, with at least 500 flywheel HP.
4-6 under full throttle....

 

it is a 93