It (the vert) turns more revs at cruising speed than the coupe. I don't think it's anything beyond that.

I definitely don't drive either car like a maniac (lol). I'm old.

 

Lugging an engine is no good, sometimes turning a few more rpms is a good thing.

Like I said I have over 2 tons 4.10s, 3800 stall, and based on performance something beyond 400rwhp. It still gets 18-19mpg be it my rural commute to work with a few stops and 55mph or 150mile each way trips to go racing INCLUDING the racing. Everything about my car should make for worse mileage than yours. If you are getting 21mpg with a stockish f-body there is a problem somewhere.

 

I don't think there's any doubt that a A4 car turning 2100rpm @ 70mph is going to get worse fuel economy than a M6 car that turns 1600rpm @ 70mph. Best fuel economy (recorded) that I've got in my '97 SS M6 was 29mpg going from Manhattan, KS to KC, KS averaging 76-78mph, so I was turning 1700-1750rpm.

 

Exactly.

I'm not sure of the M6's rear ratio, but the A4 also has the performance axle option. With that and the 4L60E's lower top gear -- it is what it is. All these guys saying they get 27+ mileage are running at very controlled specs. I've done it myself. However, i've been daily driving the M6 for the last 10 days (Avalanche is in the shop). I'm getting 21mpg per tank and my commute is 50 miles each way. 65% highway, the rest city. I baby it running 1-3-5 and still get 21mpg. The only way these cars will consistently give 27+ is at constant cruise -- on the pipe at 65-70 mph.

 

Think I figured out my highway high temp problem.The previous owner had new radiator installed at a shop.Shadetree Services must be their name.They completely removed the lower air deflector in front of the radiator support and I assume they threw it away.No screws-no broken deflector pieces whatsoever.Now why would you remove it.Does not come off to remove radiator.Will buy one and post results.Thanks for all the input.

 

Did the trick.The previously missing lower air deflector in front of radiator support cured the high temp.Now with 180 stat and pressure tested (found 2 hose clamps leaking) at 25 psi for 30 minutes.The car now runs 180-185 in town with a/c on high.It runs 175-180 after 20 minutes on the interstate at 72 mph with a/c on high.There ain't nothing worse that watching the temp gauge more than the road.I will give it a week or 2 and make sure all is good.Oh forgot to mention my new Autozone 18 psi radiator cap leaked at temp.I let it cool and removed and installed it again and now is sealed.This is their store brand made in frickin Guatamala or somewhere.Will return it for a stant.Next will check fuel mileage and report if temps make a difference.I am assuming will help to be 180 instead of 210.Might cure some of the rich burn.If not will get someone to scan the ancient obd1 to see if o2's are faulty.Again thanks for the input.This is an awesome message site.I have learned an awful lot about 4th gen z28's since I bought my first 1995 m6 last September and my most recent 1994 a4 in July.And I used to be a FORD guy.

 

94+ M6 cars all came with 3.42 from the factory.
If your A4 is a performance axle option, it should have 3.23.

For as little as I drive my car anymore I don't take it easy and try to conserve gas mileage.

 

This should help. The PCM will go into enrichment mode when the temps get too high (105*C I believe, which is about at the half way point on the gauge), and engage the an enrichment mode at all throttle positions in an attempt to save the engine (rich mixture is safer than lean or Stoic). This will do bad things, like fouling the O2 sensors and overworking the cats. I'm not sure what it does to the fuel trims, but it might be worth it to unplug the PCM fuse for a minute to reset the computer (of course if you've already driven it a few days, it won't matter).

For what it's worth, I've never gotten great mileage out of my A4. It's been a daily driver for years and I keep track of every fillup and track mileage, and it's real hard to break 20 MPG in mixed driving. I often travel from RI to Lake George NY which is about 220 miles for me, and I get a consistent 21 MPG on the trip up (which is uphill most of the way, sea level to ~1800 ft, so it's not too bad, just not great), REGARDLESS of speed, whether I go 65 or 80 with traffic. It doesn't ever seem to matter, speed, tire air pressure, fast or slow acceleration, or bolt on mods.

Ethanol fuels are crap, that's for sure. I've estimated a 10% drop in mileage for a 10% blend but it's hard to see that anymore for testing, non-ethanol fuel being scarce these days (some stations in VT have it!). I am not looking forward to the upcoming 15% blends and expect mileage to continue to drop.

Best mileage I ever got was 24 on a trip back from FL, which was literally run on a flat stretch at a constant speed until out of gas, pull 1/10 off the highway into a gas station, fill up, then drive again and repeat. I'm happy these days with 20 MPG overall, family's fancy CVT 4 banger econo-subaru and ecotech-engine 6-spd Malibu are only averaging 25 mpg, so I'm really not doing too bad for a 150k mile '95 5.7 liter 4-spd.