I mean nobody ever said anything about wanting high gas mileage I just asked if my mileage was normal or indicative of an issue I needed to troubleshoot. Had I complained about gas mileage your comment would at least halfway have a basis making sense but since that isn't the case it just didn't really get any traction. Not sure why you or anyone would get emotional over what I said but then again 2020 seems to be the year for everyone getting in their feels about anything and everything haha. Its all good though. I am going to look into the 02 sensors and try the bgk44 stuff. I've heard lots of people say it works great and isn't snake oil. Either way its worth a shot and isn't expensive by any means.

 

Yeah the reality is that a drop in fuel mileage could be anything it’s like saying “why is my engine hot?” or my favorite “Why do I have a rough idle?”. If there are no codes then you need to get a scanner and start looking for unusual readings, anything else is a guess. O2 sensor is a good guess but so would be a flakey CTS or TPS or MAP or EGR, etc, etc. And I don’t think anyone is getting emotional here ( I’m certainly not) but without scan data and more info these suggestions are just that suggestions.

 

Yeah and your corvette is a lot lighter than my SS (it’s about 1800kg). My mileage is similar on the big roads and that’s loaded up with the family. Speed doesn’t seam to effect it either I guess that’s the advantage of a large V8 with a 6 speed box.

 

What's your typical speed like; if you drive an A4 it won't get TC lockup till slightly over 40mph.
With the TC unlocked mileage will be lower than with it locked.

Most local driving is 40mph with some 30mph zones. Unless I run up to TC lockup mileage will drop off by a few MPG.

It's all about engine speed vs wheel speed if steady speed driving.

Of course one must factor in those moments of "spirited driving", after all it is a Vette.

 

If they are original, your fuel injectors are 27 years old. A rebuilt set of Bosch 3's would probably fix problems you don't even realize you have.

 

I get about 16/25 with my 6.0 ls swap w/ 220/224 cam. What the OP is getting is great IMO.

 

There are so many variables in city driving it is hard to state what a "normal" mpg would be. Cold starts and short trips, stop and go traffic, how hard you accelerate, AC on of off, etc.

A more consistent and comparable with others would be a highway drive on level ground on a calm wind day. Many of us have taken trips where this is the case and have something to compare and see if your mpg is within reason .

However, I have had some cases where my mileage dropped. The most common for me was a failing O2 sensor. They can deteriorate and slowly change to bring down the mileage. Less common are other sensors.

I have also found a couple of oddities. On my '95 I had a change where mpg dropped over one tank of gas. After several more tanks it did not return to normal. I tried to check what I could, but I accidentally found that disconnecting the battery worked. I suspect that I had some bad gas and the computer learned the adjustments for that gas and disconnecting the battery caused the learned data to be erased. It did not change the programmed tune, but caused the computer to relearn the new conditions. It is not too likely that will have such an impact on many people's cars, but it worked for mine that time. It is now a point for me to disconnect the battery and cause a relearn after changes.

I also have a '96 that I thought was running pretty well. However, I took a long trip in it (over 1000 miles). As I drove it on the highway the mileage improved after about 300 miles. I don't know the cause, but it helped.

There can be a lot of items to make a change in mpg. All of the sensors, spark plugs, computer and tune, exhaust restrictions (I had a nearly plugged catalytic on one), weight of oils, temperature (it is always 2 or 3 mpg less in the winter), ethanol blend vs pure gas, etc.

I also have a C5. My C4's get very nearly the same mpg but the C5 might have a 1 or 2 mpg edge.

Good luck.

 

my 84 crossfire get about 15 in city and hi way about 19 and i run rec fuel not bad for 35 year old car

 

I know you arent getting emotional and that is why what I said wasn't directed towards you. There is more cause of assumption that buccaneer was being emotional in his response than there was for his comment to apply in any way to myself based on the initial post. But none of that really matters either way. I see what you are saying. I havent found any codes with scanner and no pop ups on the dashboard. It could very well be anything you mentioned. I tend to hear a lot about the O2s which gives me an educated guess if where to start. I've also read and heard about the MAPs being a likely culprit. I will start with those two areas first. And see what I can find. I appreciate all of the feedback from everyone.

 

If you can get a scanner that works for you that will be the best way to resolve any issues going forward. When I got my car it was running rich but no codes. When I could actually see the sensor valves I could see why the ECM kept commanding more fuel. There are plenty of people on here who will discourage the replacement of sensors without careful diagnosis, they are absolutely correct however I’m a little more pragmatic. These sensors are old and they are cheap so I see no problem with replacing the O2 or the MAP or whatever but it’s nice to know what change it actually made and you can only do that by measurement. Oh and Buccaneer is a good guy and very helpful. I have one of his Renegade intakes on my 84 and every time I pull the trigger on that car a way a little thank you to him.

 

I"m retarred here in Floriduh.....so my '72 hotrod vette gets about 17-18 or so on the trips to the store a mile away....maybe 5 total round trip.....engine hot by time into the garage......~5000 miles in TWO years of 'driving'.......last check, and if anything, it's less now....one the road years ago, with the DPFI/computer/closed loop the thing got an easy 24+ doing 80 up/down I95

I BET today it could/would get an easy 28mpg on the freeway.....cruising 80 and getting passed.....