Gas Mileage Findings
 

Hello everyone. I just make a 1500 mile drive from PA moving to FL in my 8. I kept record of all my gas mileage price of gas etc and thought some ppl who are searching the site looking for some figures could find these interesting.

1st fill up. $47.51 at $3.97/gal 93 octane=24.2mpg windows up no A/C
2nd fill up. $42.50 at $3.99/gal 93 octane=24.31mpg windows up no A/C\
3rd fill up. $52.50 at $4.13/gal 93 octane=21.23mpg windows down/ some A/C
4th fill up. $48.00 at $3.98/gal 93 octane=21.33mpg using mostly A/C
Final Fill up.$51.01 at $4.21/gal 93 octane=22.17mpg using some A/C

All these figures are on mostly highway and 72mph in 6th to keep the rpm's under 3750. Some have slow traffic/ above the 3750 rpm but I was very pleased with the 24 mpg but do see a 2mpg difference with a/c and windows down.
Hope maybe this helps anyone looking for some gas mileage info.

not bad at all. I usually get 20-22 on trips but I cruise at like 80 and do the occasional 3rd gear drop :) Best Ive seen from an 8.

bet it would have been more with 87 oct.. but good job..

btw, if you need any help i am just a pm away..

beers :beer:

i would kill for anything even near those numbers, 15-16mpg for me, no matter how I drive.

:(

higher w/ 87 octain how?.. premium 91 plus you will get better gas mileage then lower octain gas

really..

bet you are wrong..

beers :beer:

1) It's "octane"

2) You can use whatever grade octane you can get away with that doesn't cause engine knock. For instance, if you can run on 89 octane consistently w/o knocking, bumping up to 91 or 93 octane won't net you much if any gains in mpg. You might get a few more horses out of the higher grade, but mileage won't be noticeably better.

Some people are swearing up and down on 87 octane + premix, whatever works. Other's have reported down grading their gas and getting knocks, rough idel, and an occasional check engine light. I'm not interested in finding out what grade I can jump down to as my car seems very content on the expensive stuff. Especially considering this engine is known for carbon build up which can cause knock with lower grade fuel.

This was a good read:

http://www.wisegeek.com/what-is-high-octane-fuel.htm

Considering that the RX-8 has a 10:1 compression ratio, I found this part interesting:

Ok I put in 93 because thats what i feel is the best for my car. I did not start this thread to say which is better thats just what I did and some ppl live by 87 some by 89 91 or 93 but with 93 I get a couple tenths to a gallon less maybe 1mpg at the most compared to 89 but the performance I feel I gain is worth that 1mpg.....

if you are comfortable running 93 then run it. it's your car.

i'm going to try lower octane gas next time w/o premix to check the mpg. right now my tank looks like its going to last me some 160 miles (80 miles on exactly half a tank)... this is 93 shell with 5oz of idemitsu.

higher octane will not improve MPG............................

higher cost must mean there's more gasoline per gallon!

Each state has a different formulation of gasoline. Many times different formulations within different regions within the state. Some of these specify different levels of alcohol and others additives for emissions reduction. Alcohol can be used to boost the octane rating of gas, but it has less energy than straight gas. So, in this case, high octane fuel could produce less power and mileage than regular.

Lately I have been getting around 21 mpg on my way to and from school, which is mostly back roads, shifting at 3,500 with the occasional redline.

octane is basically resistance to preignition. If you aren't knocking, you can go down as much as you'd like. Most report better mpg with 87, including myself.

I run 93 now because of the turbo. Compressed hot air = easier to preignite, so the higher octane prevents engine damage.

Using a higher Octane does not get you better gas mileage. The higher the octane means that it will burn at a higher tempature.

Your car spray's the exact same amount of gasoline into the chamber to be burned no matter if your running 87 octane or 118 octane. The only difference is that the 87 Octane will ignite at a lower tempature. The higher the octane, the harder it is for your car to "knock". Knocking is when your gasoline ignites before it should, causing damage to your engine.

Cars which rev high (Rx8's/ Honda Vtec )and turbo cars call for gasoline with a higher octane rating so that when the engine internals become hot from extreme use, the gasoline does not pre-ignite and eat ur engine.

An example that I relate to is my friend who has an Acura Rsx-S. His Rsx calls for premium octane but when were on the interstate or traveling and not beating the engine to death we throw in 87. Now if he was to go to the track we would use 93+ octane.

Mike

Interesting how different is your tone about this topic than a few days ago when you were pretty much calling people idiots for using 87 :)

I don't think I'd be able to get that low fuel mileage if I wanted to... the worst so far was 210 miles before I had to fill up and I was beating on the car a lot during that tank, plus drove 80% in city traffic.
Something is not right with getting just 80 miles and the gauge being already halfway down...

For three years, I've been listening to a handful of owners complain of getting this kind of mileage. Unless they're crazy, I don't see how it can be done. I usually get 230 miles or so per tank.

I didn't call any one names from what I can remember (maybe just cheap skate :uhh: ). I just don't personally want to take the chance of getting engine knock. If you can run 87 w/o problems, good luck. I'm not brave enough to find out. I'm also coming from the turbo world which is where my fear of low octane knock stems from.

However, from what I read on this forum, not every RX-8 is content w/ 87. Some people have mention rough idles, pinging, and the dreaded CEL. Since my car is strictly driven for fun on the weekends, I'm not interested in finding out if my car is happy on 87.

lol, Im not trying to be a savior, I just follow the owners manual. 91 octane, 5w20, etc. Running healthy at near 70K in an 04. Thats just me, I respect everyone elses methods. IMO it doesnt matter as long as the engines healty :)

I am about to get 240 on the tank. I swear mobil has the best gas I usually pumpnat 7 11 and get 205 a tank and 180 in the winter. But I don't live nearva mobil station or I'd pump there more often. What's the highest some ones ever got on a tank 240 here :)

I'm going to pose a new question because the Worst MPG I've gotten was around 15. I do a lot of highway driving around 75.

What is the worst mpg you all have gotten under "spirited" (tirerack) driving? When you all autocross, whats that look like with high rpms and hard driving?

Just curious.

I run 93 w/ a just a splash of premix for each tank - Just to keep it interesting. The best mpg i've gotten was 22mpg, got 330 miles on 15 gallons. But that was no A/C, no windows/sunroof and babying the crap out of it.

if you're doing a lot of hard acceleration non stop on a track, you should be able to achieve 4-6 mpg range.