> 87 octane vs hi-test
I am 99% sure all engines today have knock-sensors. If you put low-test in a "hi-test" engine, it senses pre-detonation and pulls-off some advance. You get less than rated power. This may be fine for you 360 days a year. When you plan to trailer, load up on hi-test.
I am 99% sure all engines today have knock-sensors. If you put low-test in a "hi-test" engine, it senses pre-detonation and pulls-off some advance. You get less than rated power. This may be fine for you 360 days a year. When you plan to trailer, load up on hi-test.
Yup, my '02 Altima V6 will still run on low octane (93 is specified in the manual), but along with noticeably poorer performance, the fuel economy takes such a hit that it almost negates the cost savings.
It's a lot more fun to drive with the hi-test anyway - that old sedan will still do 0-to-60 in about 6-1/2 seconds, and that's with an old fat guy at the wheel!
It's a lot more fun to drive with the hi-test anyway - that old sedan will still do 0-to-60 in about 6-1/2 seconds, and that's with an old fat guy at the wheel!
> fuel economy takes such a hit
If you mostly drive part-throttle (half manifold pressure), it shouldn't. You need octane when the engine is breathing full and the peak pressure is high.
> my '02 Altima V6
OK, I admit my '02 Accord's ECU is not the smartest chip on the block, approximates some conditions which could be better balanced with more smarts.
If you mostly drive part-throttle (half manifold pressure), it shouldn't. You need octane when the engine is breathing full and the peak pressure is high.
> my '02 Altima V6
OK, I admit my '02 Accord's ECU is not the smartest chip on the block, approximates some conditions which could be better balanced with more smarts.
In 2015 I got the Escape and in 2018, the Edge. Every night, I read one chapter then went down to try out what I had just read. Thank goodness I had the stepping stone of the Escape (mediumly equipped), three years before I got the Edge (all bells, all whistles). The manual is 550 pages. I still can't believe all the things cars do nowadays. I've never seen things like air bags built in to the rear seatbelts, ambient lighting, air conditioned seats and autonomous driving.
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Our 100% gas costs about 10% more than the adulterated 87 octane gas, but I get 10% better mileage with it,
and the car runs better, so it's good.
Engines with boost need high octane gasoline. They were designed for it.
Yes you can run regular in them and the computer will try to compensate, but it was not designed for low octane gas and it is a compromise which should only be done in emergency (as in you can't get hi-test).
Pollution goes up as the engine de-tunes itself for lower octane. Retarding the spark throws off the efficiency and the cylinders run hotter. Even in a water cooled engine, it will throw off the operation of the engine.
This is a bad plan all around.
I modified my 1975 HD Sportster by dual plugging the heads and running dual-fire ignition. This allowed me to continue running regular gas with the compression adjusted to 9.4:1 using different thickness head gaskets. The engine runs strong and fairly clean based on exhaust gas smell. I have not put a sniffer in the exhaust.
This is just my opinion. YMMV
Ethanol causes air cooled engines to run hotter than straight gasoline. This is bad for an old air cooled engine like the Sportster, and is a justification for running low octane gas with proper modifications.
Yes you can run regular in them and the computer will try to compensate, but it was not designed for low octane gas and it is a compromise which should only be done in emergency (as in you can't get hi-test).
Pollution goes up as the engine de-tunes itself for lower octane. Retarding the spark throws off the efficiency and the cylinders run hotter. Even in a water cooled engine, it will throw off the operation of the engine.
This is a bad plan all around.
I modified my 1975 HD Sportster by dual plugging the heads and running dual-fire ignition. This allowed me to continue running regular gas with the compression adjusted to 9.4:1 using different thickness head gaskets. The engine runs strong and fairly clean based on exhaust gas smell. I have not put a sniffer in the exhaust.
This is just my opinion. YMMV
Ethanol causes air cooled engines to run hotter than straight gasoline. This is bad for an old air cooled engine like the Sportster, and is a justification for running low octane gas with proper modifications.
The Ironhead Sportster (1957-1984) had hemi heads with the plug offset to one side. No matter what plug you use, the flame front has to propagate over center and down the opposite side of the chamber. Adding a second plug opposite the first gives superior ignition and flame propagation for this chamber.
On trips of a few hundred miles, The Volvo XC-90 gets a mileage boost/economic benefit slightly greater than the cost of upgrading to a higher octane mix, the Ford Expedition gets no such benefit -- both are great when you get those awful icey roads through the hills of PA's version of I-80.
The Volvo is mostly driven by wifey and she requires new brakes so frequently the cost far outweighs any benefit from higher octane!
The Volvo is mostly driven by wifey and she requires new brakes so frequently the cost far outweighs any benefit from higher octane!
My e90 BMW says 91 octane recommended, min 87 octane but I always use premium because I use the throttle at times 
It's fuel economy is crap in the city, but it's not slow, either. Come to think of it, it uses just a little more than my old 84 VW which i drove wide open most of the time at least to get up to speed. Right now I'm averaging 13.5L/100km/h with an 80% stop and go city and 20% highway pattern. When I reset it and drove from Toronto to Montreal, I got about 8L/100km/h or so...
It's fuel economy is crap in the city, but it's not slow, either. Come to think of it, it uses just a little more than my old 84 VW which i drove wide open most of the time at least to get up to speed. Right now I'm averaging 13.5L/100km/h with an 80% stop and go city and 20% highway pattern. When I reset it and drove from Toronto to Montreal, I got about 8L/100km/h or so...
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My 95 Peugeot 306 S16 specifies minimum 95 RON, but I guess at 10.5:1 compression ratio it needs it... It does have a knock sensor but still the spec is no lower than 95...
I only run 98 in it though. The difference in responsiveness is about the same as a whole gear (ie running 95 you would need to be one gear lower to get the same pickup as one gear higher with 98). It's not subtle.
I guess it largely depends on the engine and the computer.
In aus the lowest we have is 91 RON.
Tony.
I only run 98 in it though. The difference in responsiveness is about the same as a whole gear (ie running 95 you would need to be one gear lower to get the same pickup as one gear higher with 98). It's not subtle.
I guess it largely depends on the engine and the computer.
In aus the lowest we have is 91 RON.
Tony.
There's a thread about that ...Then somehow managed both times to forget to order a part I need...
