MosesX605

I average just under 17mpg for predominately city driving and just over 27 mpg on the highway @ 75mph.

bizarro

iTrader: (1)

I think I read somewhere that regular gas is good enough and premium is just overkill no matter the condition unless it involves a turbo...I use regular on my 13b and haven't had a prob that was fuel related...

smnc

Superchargers and Turbochargers both require octance to prevent pre-detonation or "pinging" of the engine.
N/A rotaries actually prefer a lower octane fuel, so any GOOD 87 octane gas should be fine...

LongDuck

What you heard about fuel economy and using 'High-Test' (high octane) fuels is correct. The rotary engine does not require a high octane fuel to run correctly, in fact, using a high octane rate pump gas could lead to overheated exhaust temperatures (cats), clogged cats, or even problems with backfiring. In the mid to late 80's all IMSA RX-7 wins were with 85-87 octane pump gasoline - and this usually had to be brought by the racer, as they couldn't get that LOW an octane at the track (reference Racing Beat catalog and Mazda Performance Handbook). Here's why;

The rotary engine has a very short burn cycle for the amount of power that it produces. This is due to the short distance and short time that the flame front is traveling across the plugs, and into the power and exhaust phases of combustion. Octane is added to fuels to actually slow the rate at which they burn, which, while reducing 'pinging' or precombustion (detonation) in piston engines, unfortunately causes not all of the fuel elements to be burned in the rotary engine during the power and exhaust 'strokes'. The end result is that you get unburned fuel in your exhaust, which then either gets burned in your catalytic converters, or results in backfiring and flaming tailpipes when this unburned fuel meets with hot exhaust and/or fresh air (carrying oxygen). Excess gas (an overly rich mixture) can be good for the engine only in that it reduces combustion temperatures since not all fuel is being burned, the unburned fuel is absorbing heat, but the downside is inefficient combustion - which robs power.

The thread discussing this came up when a club member here couldn't pass emissions. Once he did a minor tuneup and dropped DOWN in octane rating, he was able to pass emission testing without any problems.

The fuel manufacturers would have you believe that 'high-test' gas is good for everyone, but racing history, and practical use dictate the use of 'standard' fuels for your rotary engine. Take this as yet another nice feature of driving a rotary car in that you will pay less at the pump for your driving enjoyment.

MosesX605

Yeah, our gas mileage may not be the best, but my friend's Supra takes premium because he has the high-comp motor. The ten cents a liter difference more than offsets my 12A's thirst compared to the straight six.

mmasid

I get 18 city and 27 highway. I track my mileage so close that I drive down to the last half gallon quite often just because I hate stopping at the gas station.

oni-dori

haha... so that's why my cat was so messed up. i was driving one day and all of a sudden, i let off the gas and a horrible clunking sound came from underneath the car. at first i thought something came off. i got underneath the car and tried to look for it. nothing. so i took it to the muffler shop and had him take off the cat. bingo, all the bricks inside fell off. i ran 91 octane when i first got the car 3 weeks ago and before i knew about this. now, its pure 87.