mn__30

By the way? What octane fuel do you guys use? I use 87.

wedley2

my friend uses premium and gets around 500. '02 special edition, 14k.

98CoupeV6

Your friend is wasting about $.20 a gallon every time he fills up. It's been proven through dynos and through various tests that you should always use the specified octane for your car. The only engine that I know of that is an exception is the 240HP 3.0L V6 in the 2003+ Accord, which advances its timing when premium fuel is used. Do a search...people need to understand what octane rating means.

500 on what? 15 gal, 16 gal?

MrChad

I have graphs I did in MS Excel early on when my car was newer...I know--stop laughing now.....

In anycase, the two biggest things that improved my MPG. Synthetic oil, this gained me a solid 1-2 MPG easy. I also gained 1-1.5MPG using Premium fuel...however this didn't offset the price of the fuel...can't say if it helped the HP either but I speculate not. I'm not sure why the fuel helped but I think it's slower burn rate gave it better milage in my case....

Now, the Synthetic oil also keeps the entire engine in shape so it's cost was well offset IMO, but the premium fuel....I'd just buy the lowest (cheapest grade) you can get by with per mfg. recommendations. This however doesn't mean I go to the cheapest priced stations...I stay away from unfamilier no name stations for fear of watered down or bad gas...just my 2-cents.

98CoupeV6

Premium fuel adding MPG doesn't make since since it lowers engine output...Road and Track dyno tested a bunch of cars a few years ago including the J30A1 Accord and every single one lost power when you put in fuel that wasn't what the manufacturer recommended. I wonder why you got better MPG? It would stand to reason that the less efficient your engine is, the less MPG it's going to get...maybe I'll try a tank of premium just to experiment.

BTW, what oil do you use?

motoguy128

The above post is correct. In almost every case, high octane fuel used in a engine that does not recommend premium will result in lower mileage.

Simply put, in a engine designed to run on 87 Octane, higher octane will effectively retard the timing. Higher octane fuel is needed in some high performance engines because lower octane fuel ignites too soon after the spark, and will cause knocking. Knocking is when the gasses from combustion begin to expand before the pistion reaches the top of it's stroke. But if igniton occurs too late, soem of the energy form combustion will be lost, resulting in less power being transfered ot the crank with the same amount of fuel burned.... that equals lower fuel mileage.

wedley2

15 gal i believe, his mom pays for everything, car payments, insurance and gas. so its no loss to him

MrChad

Well I had the better MPG on 3 or 4 tanks, not sure why but I did? I did my best to make sure it just wasn't my driving that week(s). The hgiher octane gas gave better MPG. I'm not sure the F23A1 is smart enough to play around a bunch with timing, I wasn't even sure if the block had a knock sensor maybe it does.

I use Castrol Syntec 5w-30, I use to use 5w-50 but couldn't see the point. I have some friends that love Mobil 1 and others that love Amsoil. I use Syntec because at the time it was the easiest to find. And I don't switch brands once I have started. I also use the standard Honda oil filter, I use to use Mobil 1 filters as well but again I didn't think it was needed with my frequent oil changes.

98CoupeV6

Hm, very interesting. Theoretically it shouldn't give better MPG.

I use Syntec 5w-30 as well...great stuff. I use 10w-30 in warmer months where the temp doesnt fall below 40, as specified by the service manual. 50 would give better gas mileage but probably wouldnt lubricate the engine as well, right?

motoguy128

50 is heavier weight oil.. ie higher viscocity. It should give LOWER mileage but protect better in hgiher temperatures... and actually protect less at lower temperatures... despite the 5W rating.

Lower weight oils will give better mileage. That's why never cars recommend 5W30, 5W-20 or 0W30.

Protection is equal at operating temperature so long as the oil doesn't overheat.