24 mgp???
Thread Starter
Racer
Joined: Mar 2008
Posts: 362
Likes: 2
From: denton tx
24 mgp???
I have only been averaging about 24 mpg hwy @ 70 mph. This is only about a 10 mile run. Not a DD weekend only. A4, 315, dual cone K&N and, borla exhaust. I have noticed the tail pipes have a little soot build up. Is this from only driving on weekends? Do I need to "blow it out" every now and then? Would new plugs and wires help? I have not pulled any plugs yet to check the gap. Thanks for your input.
kj
kj
Melting Slicks
Joined: Aug 2003
Posts: 2,786
Likes: 7
From: Iowa
24 is alittle on the low side but for an A4 it might be normal. how many miles on it? the plugs are rated for 100k, but most here will say change them at 50k. it never hurts to get the RPM's up high get the cob webs out if you don't drive it often.
also, 10 miles is more than enough, but expect poor economy when the engine is cold. if you are resetting your mpg average counter right after startup then only driving for 8-9 minutes you have the abnormally poor economy of a cold engine factored in without much closed loop operation to give you more accurate readings.
also, 10 miles is more than enough, but expect poor economy when the engine is cold. if you are resetting your mpg average counter right after startup then only driving for 8-9 minutes you have the abnormally poor economy of a cold engine factored in without much closed loop operation to give you more accurate readings.
Le Mans Master
Joined: Sep 2007
Posts: 7,604
Likes: 8
From: Belleville Il
Being a 99 you are quite likely a candidate for new plugs. I'd also check your MAF and throttle body to make sure they are clean. On your MPG readings,are they off of the DIC ? Was the reading from the start of a fresh tank fill ?These things do make a difference. The best way to get an accurate Idea is to fill up ,reset everything and go out and put about 100 or 200 highway miles go back and refill , and then do the math as the DIC has a tendency to be about a mile and a half "happy" on it's average MPG. I just did this with a 240 mi round trip and had the DIC say 30.3 average,but the real #s were 28.72. This should give you a reference point. Mine is a 2000 FRC with a fresh set of plugs & wires a blackwing intake and Corsa touring exhaust.
Thread Starter
Racer
Joined: Mar 2008
Posts: 362
Likes: 2
From: denton tx
maf and throttle body are clean. i also just cleaned and oiled the filters (not to much oil) yes it was off of the dic with a fresh tank and everything reset. i should get about 80 miles in tomorrow mixed city and highway. i also purchased msd wires and gm ird. plugs and a fuel filter. i will be doing all of this in the next few weeks.
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Does seem a little low on the mpg. New plugs and wires probably wouldn't hurt.
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Pro
Joined: Oct 2004
Posts: 538
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From: Edmond Ok
I have a 3:15 axle, auto. I get right at 25 mpg actual on long distance highway. >300 mile
Your probably about where you should be. I wouldn't worry about the plugs for a while, unless you just want to. You just need to run it at full operating temperature more.
Good luck
Your probably about where you should be. I wouldn't worry about the plugs for a while, unless you just want to. You just need to run it at full operating temperature more.
Good luck
Drifting
Joined: Jun 2006
Posts: 1,730
Likes: 4
From: Delray Beach Florida
i have a 98, stock rear and a4 tranny. shorty headers b&b bullets, vararam and hypertech. changed my plugs to ngk tr55's. I make 34mpg at 70mph
like everyone sayed check your tire pressure, change your plugs and wires. clean your air cones, check your maf or build up. also i'd say blow it out every now and then, couldnt hurt lol.
like everyone sayed check your tire pressure, change your plugs and wires. clean your air cones, check your maf or build up. also i'd say blow it out every now and then, couldnt hurt lol.
Racer
Joined: Jun 2005
Posts: 438
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That sounds about right to me. I also have an A4 wit 3.15:1 gears.
Sure, if I reset the DIC at an entrance ramp and then log the mileage as soon as I leave the highway, then I'll get about 28 mpg. That's driving conservatively.
That's rare, though. 80/20 driving yields about 24 or 25 mpg. Mine gets good highway mileage, not good city mileage.
What's your average speed on the DIC? You'll be surprised how a long trip spent mostly at 70 mph will end up averaging 45 mph because of time spent idling at lights, and slow moving traffic, etc.
One final note. I don't know about you, but my DIC frequently over estimates my gas mileage. It's usually about 1.5 mpg or more high. When it says I've gotten 29.X, then I know the hand calculation will almost certainly come out to 28.
Sure, if I reset the DIC at an entrance ramp and then log the mileage as soon as I leave the highway, then I'll get about 28 mpg. That's driving conservatively.
That's rare, though. 80/20 driving yields about 24 or 25 mpg. Mine gets good highway mileage, not good city mileage.
What's your average speed on the DIC? You'll be surprised how a long trip spent mostly at 70 mph will end up averaging 45 mph because of time spent idling at lights, and slow moving traffic, etc.
One final note. I don't know about you, but my DIC frequently over estimates my gas mileage. It's usually about 1.5 mpg or more high. When it says I've gotten 29.X, then I know the hand calculation will almost certainly come out to 28.
Last edited by 71vetteinva; May 18, 2008 at 09:06 AM.
Pro
Joined: Sep 2007
Posts: 735
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From: Bucks County Pa
Gas Mileage
Hi, Gas mileage can depend on many variables. Gas quality, psi in tires, wind conditions, weather in general, temps, humidity, windows up or down, top up or down, state of tune, type of driving, even a higher amount of ethenol will decrease gas mileage by a few percent. . Also using the DIC to determine gas mileage is not very accurate.
My 03 vert, 315 rear, auto, averages a strong 29-31 on the road at speeds keeping up with traffic. A mix of 50/50 city/ highway yeilds a strong 25, while mostly city will usually drop it to around 22. The car is bone stock, oem tires have 29psi, and about 15000 on the odo. I use either Shell premium, or Sunoco premium. I measure the mileage by figuring the mileage driven on the odo, and the gas used at fill ups to get an average, and the DIC is usually way more optomistic.
Good Luck
Edit- Also I might add that the Vette is the most economical of my cars which include a Subaru Outback, and A Chrysler 300. It is fabulous to have the neck snapping performance and handling of the Vette and still get reasonably terrific gas mileage.
My 03 vert, 315 rear, auto, averages a strong 29-31 on the road at speeds keeping up with traffic. A mix of 50/50 city/ highway yeilds a strong 25, while mostly city will usually drop it to around 22. The car is bone stock, oem tires have 29psi, and about 15000 on the odo. I use either Shell premium, or Sunoco premium. I measure the mileage by figuring the mileage driven on the odo, and the gas used at fill ups to get an average, and the DIC is usually way more optomistic.
Good Luck
Edit- Also I might add that the Vette is the most economical of my cars which include a Subaru Outback, and A Chrysler 300. It is fabulous to have the neck snapping performance and handling of the Vette and still get reasonably terrific gas mileage.
Last edited by bestvettever; May 18, 2008 at 10:54 AM.
Tech Contributor
Joined: Dec 2003
Posts: 19,384
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From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
If its any help my 02 is almost the same mileage as yours and is also now a weekend car. Even as a DD in Vegas I didnt do much better than 21-22 around town. I get about 25-28 on a run.
I get 20 mpg through the back roads but because its only out occasionally, my driving is a tad more spirited than it used to be. 95 (91) or 98 (94) octane doesnt seem to change the mileage either.
Its still the same since I changed the plugs and wires.
Sounds OK to me.
I get 20 mpg through the back roads but because its only out occasionally, my driving is a tad more spirited than it used to be. 95 (91) or 98 (94) octane doesnt seem to change the mileage either.
Its still the same since I changed the plugs and wires.
Sounds OK to me.
Drifting
Joined: May 2005
Posts: 1,566
Likes: 52
From: Colorado Springs CO
Without reading the rest of the posts in advance, I had this same problem after installing my Bullets (not just because I was stomping on it all the time!!). I have a bit of soot build up, too, and this is simply due to the change in air/fuel ratio with a change to the exhaust system. The computer will "relearn" after an intake change or exhaust change, but the only thing that will fix your ratio is a good old fashion tune. The A4s benefit greatly from a tune anyway, but I think you will see this will eliminate the soot and you'll see an increase in mpg as well.
Cheers!
Glen
Edit: Also, I just changed out my plugs AND wires not too long ago, so that wasn't a huge factor in my mpg.
Cheers!
Glen
Edit: Also, I just changed out my plugs AND wires not too long ago, so that wasn't a huge factor in my mpg.
Team Owner
Joined: May 2005
Posts: 23,682
Likes: 9
From: Flagstaff Az.
I think its a little low. I picked up my vert( 04a4 with 3:15s) in Fla. and drove it here to Az. A tad over 2,000 miles and averaged a little over 31 mpg figuring on fill ups, not the computer. With all the mods now, I still get 26 on the road and 22 around town.