Fuel Economy for your Turbo Regal, getting 17.6 MPG here...

[bison]

Stock GN back in 1994 i got 24-25 highway. About 10 years ago with 9:1 CR, 200/200 cam, LU converter and ***** foot i got 30mpg. Last week i averaged slightly over 20mpg with my blue car cruising around 65mph. It has an XFI and less than 8:1 CR with a 212/212 and PTC 9.5" I was cruising at 15.2:1 and 44* advance. Actual mileage would have been higher but i sat in traffic for over an hour idling away. If you had 9.5:1 and a very small close to stock spec roller cam and lockup with lean cruise you would get closer to 30mpg highway if you drove 55-60mph. Routinely these cars get terrible mileage. Around town mileage will be crap and if you have a heavy foot you will really kill the mpg. My daily driver Park Avenue gets over 30mpg on the highway. Same displacement. The Park Avenue has a lot less rolling resistance and with a higher CR and tiny cam it has a huge advantage over a 25 year old g body with low CR and cammed to make power. I have never seen any benefit/loss running various injector sizes.

 

[slow305]

Not to mention the higher drag coefficient of the Regal compared to the Park Avenue. It literally becomes exponentially less efficient the faster you go. I would think that 50mph (right after the converter lockup at 45mph) would yield the best results (along with lean cruise), although there are not many places where you can go 50.

One of the largest areas causing drag is the area right behind the rear window. I wonder if the MC Aerocoupes are any better at getting though the air. Maybe putting vortex generators on the roof would help cut down on drag (like on the Evo's)?

Vortex generator - Wikipedia, the free encyclopedia

 

[bison]

Not to mention the higher drag coefficient of the Regal compared to the Park Avenue.

Rolling resistance includes coefficient of drag. Ive achieved best mpg with the Park Avenue between 55-60mph and the GN's around 55mph. The wind resistance isnt terrible even with a brick g body at 55mph but at 75mph its very noticeable. Ive measured deceleration g's with an accelerometer and the g bodies are terrible over 100mph.

 

[Haynesie]

Last time I calc'd I was getting about 15 on the hwy....however a few months later after it sat a while with a full tank of gas I noticed a huge puddle under it, and an empty tank of gas....so maybe my input isn't really valid

 

[Guess]

22.5 with mods below Hwy at 80 mph.

 

[norbs]

x 2 on the power logger mpg reading. I'll post it on the FT board enhancement list which is still on a backlog looks like

 

[crow]

milage

Since my buying a GN I have kept close tabs on mileage. I did it cause I got such a kick at watching the Camaros/Mustangs/Vettes pay through the nose for gas usage. It amazed me to see the 87 get 24-26 on the hwy consistently. I just could not believe it. My old Corvette gave me 12 mpg at best. The GN gave me more power and room to boot.
Sorry, I digress. 24-26 hwy and 17-19 city, burning 93 oct. I live in Central Florida and we have no hills. Hwy speeds are 70-80 mph. I checked the mileage by filling up every time and dividing miles on the trip odometer by gals. Reset the tripodomemeter after every fill up. Still do it and keep my receipts.
Just recently I made some changes in the bone stock GN. New SS 2" exhaust system, test pipe for a cat, 3.5 SS DP, TT 93* chip, Big Mouth Cold air intake. My mileage seems to have dropped. But I'm not done yet. Adding a Razor alky kit next week and tuning er up. Then I will give it a serious check.
I have been told my mileage should not change. BTW, my car has 106k miles on it.

 

[williamsGN]

Just did 18 mpg yesterday - 150 mile round trip, mostly light traffic, 70-75 mph, used the air on the way home. Mods below including a LU converter. I think for the amazingly high claims (better than the window sticker), might be time for a calculator.

 

[SCOOBY DOO]

22-23 MPG on the highway.

 

[smoke20]

23 mpg on E85 all Hwyway with a 15.4 AFR

 

[Mountain GN]

My GN has been in the family since the car was purchased back in June of 1987. I've got a log book of every drop of gas put in the car for the first 17 years of it's life.

My Dad seemed to average about 24 overall, but I could tell from the logs when he went on a long trip because he would average 30-32 MPG.

After he passed away and left the car to me, I achieved 31 MPG on he drive from Las Vegas to LA. This was a straight 65 MPH cruise, and the only mods on the car was a Kenne Bell Ram Air and a hollow cat.

Now that I've added the mods below, I average 19-20 MPG on all-highway driving. I'd really like to know where my mileage went!

As a side note, the wife mistakenly put 87 octane in the car a while back, and it picked up 2 MPG. I tried it again to see if it was a fluke, and it happened again. You just can't bury your foot in it.

 

[John Wilde]

My GN has been in the family since the car was purchased back in June of 1987. I've got a log book of every drop of gas put in the car for the first 17 years of it's life.

My Dad seemed to average about 24 overall, but I could tell from the logs when he went on a long trip because he would average 30-32 MPG.

After he passed away and left the car to me, I achieved 31 MPG on he drive from Las Vegas to LA. This was a straight 65 MPH cruise, and the only mods on the car was a Kenne Bell Ram Air and a hollow cat.

Now that I've added the mods below, I average 19-20 MPG on all-highway driving. I'd really like to know where my mileage went!

As a side note, the wife mistakenly put 87 octane in the car a while back, and it picked up 2 MPG. I tried it again to see if it was a fluke, and it happened again. You just can't bury your foot in it.

Good update, I had not considered octane...

 

[Squid4life]

We had a get together up north this past weekend and I got 19.29 MPG. This was 90% highway with one detour of about 20 miles of stop and go 25-40 MPH crap. Kept it at 72 most of the trip, only hit boost on long up hills, and then it was only ~3-5 psi. Best I have ever gotten to be honest. Most of my road trips were loaded down with about a thousand pounds of uniforms, tools, and other crap.

 

[williamsGN]

I've heard of premium gas increasing mileage, but never decreasing it.

 

[Mountain GN]

I've heard of premium gas increasing mileage, but never decreasing it.

Neither have I! I've literally owned dozens of vehicles that "take" premium, and have probably made the 87 octane mistake on each at one time or another, and this is the only one that ever returned IMPROVED mileage on 87!

 

[slow305]

I've heard of premium gas increasing mileage, but never decreasing it.

I've always believed that a lower octane fuel would net better mpg, although no long-term studies have been done. The higher the octane rating, the more resistant to burning spontaneously and completely at lower heat and compression (such as no boost in an 8:1 engine). So, putting 93 in a Geo Metro isn't going to get you any more mpg's. Since the engines in our Buicks are not very high compression (when not under boost), it would make sense that 89 would net better milage, but less overall power.

Just a theory, please chime in with thoughts.

 

[we4Mateo]

I've always believed that a lower octane fuel would net better mpg, although no long-term studies have been done. The higher the octane rating, the more resistant to burning spontaneously and completely at lower heat and compression (such as no boost in an 8:1 engine). So, putting 93 in a Geo Metro isn't going to get you any more mpg's. Since the engines in our Buicks are not very high compression (when not under boost), it would make sense that 89 would net better milage, but less overall power.

Just a theory, please chime in with thoughts.

I agree 100%. Our engines wouldn't need premium with low or no boost.

 

[TurboBob]

I've always believed that a lower octane fuel would net better mpg, although no long-term studies have been done. The higher the octane rating, the more resistant to burning spontaneously and completely at lower heat and compression (such as no boost in an 8:1 engine). So, putting 93 in a Geo Metro isn't going to get you any more mpg's. Since the engines in our Buicks are not very high compression (when not under boost), it would make sense that 89 would net better milage, but less overall power.

Just a theory, please chime in with thoughts.

I'm not sure about the low compression, but years ago the Impala SS group (NAISSO) had a bunch of people doing back-to-back comparisons between 87 and 93. 87 always provided better mileage.

The Impala engine was a 10.5:1 compression, iron-head LT1.

Bob

 

[bison]

You can run considerably more timing everywhere with higher octane and get any lost heat energy back or more. With 93 octane light load I'm running 44*. if I had better than 93 I'd increase it more. Over 50* if the octane is there. The stock chip runs timing like this under very light loads.

 

[Mountain GN]

You can run considerably more timing everywhere with higher octane and get any lost heat energy back or more. With 93 octane light load I'm running 44*. if I had better than 93 I'd increase it more. Over 50* if the octane is there. The stock chip runs timing like this under very light loads.

I see max of 44* at cruise with my TT alky chip. And this is the chip that delivered the 2 MPG improvement on 87.

My car is VERY sensitive to knock, even at low boost levels, so I'd be hesitant to have Eric bump up my light load timing anymore.