Premium or Regular?

[ALS]

I use 87 what ever is cheapest.

[Tideland Prius]

87 for me.

[Codyroo]

The analogy I was given for premium vs regular was shoe size. A size 11 shoe won't make your size 9 feet run better. But wearing a size 9 shoe on your size 11 feet will be a problem.

Maybe running uphill in the mountains while wearing "Bozo the Clown shoes" (premium) WILL make you run faster....one for the mythbusters (or Bob).

[jay_man2]

Originally Posted by Codyroo

The analogy I was given for premium vs regular was shoe size. A size 11 shoe won't make your size 9 feet run better. But wearing a size 9 shoe on your size 11 feet will be a problem.

Maybe running uphill in the mountains while wearing "Bozo the Clown shoes" (premium) WILL make you run faster....one for the mythbusters (or Bob).

Whatever size, as long as they're PF Flyers!

[bwilson4web]

Originally Posted by Codyroo

. . .
Maybe running uphill in the mountains while wearing "Bozo the Clown shoes" (premium) WILL make you run faster....one for the mythbusters (or Bob).

Not so much 'faster' as less likely to exhaust the traction battery. I've read several reports of 'I was going up the mountain at <some high rate of speed> when suddenly the car slowed down and ...' The traction battery Ahr capacity is still the same (for a new battery) and that is the only other source to maintain speed when climbing at peak ICE power settings.

Now if I've got 87 octane and I'm in West Virgina, I would keep my speed under 80 mph. But if I've got 89 octane, my lead-footed wife could drive and I would not be too worried. I don't see a need to test higher octanes unless I can find a really, really steep hill that I can climb really, really fast.

Bob Wilson

[HTMLSpinnr]

87 octane is what's recommended (despite the misprint in the Owner's Manual initially stating 88 octane).

Also worth noting, that Mid-Grade 89 is simply a blend between 87 and 91/92. This became real obvious when we were switched from 92 octane to 91 octane in the west, and gas stations had to relabel mid-grade from 89 to 88.5 octane w/ temporary stickers until they could get their mixing valves readjusted.

[UncleMark]

I love how people read their owners manual about what grade of fuel to burn. The 87 octane regular on the flat lands is reduced to 85 octane in the mountains because of the altitude. If you're unsure call your dealer. I drove my 87 octane car thru the Rockies using 85 octane and never had a problem. I alswys use Shell, BP, or Phillips 66 gas whenever I can get it on my trips. I had a rental car back in August in KS (a 2009 Yaris) and got 40 mpg running 70 mph on I-70 with the A/C on using Phillips 66.
UncleMark

[bottomfeeder]

Originally Posted by qbee42

It is not only unnecessary, but it will reduce your gas mileage. Premium gas is only an advantage in engines designed for premium. Why not try diesel fuel, as it has more energy per gallon? The answer to that is obvious: the Prius engine in not a diesel. While using premium gas isn't as silly as using diesel, the same concept holds true. Use the proper fuel for your car. In the case of the Prius, this is 87 octane (85 at altitude).
Tom

Actually, the energy content of premium is slightly higher than regular. If anything, one should get better mileage with premium, however, the difference is small and hard to accurately measure--and probably not enough to offset the price difference.

The 2010 Prius has a high compression engine (13:1), but like all new engines these days, has knock senors that will cause the ecu to retard the timing when burning regular fuels. There is a performance hit when doing this, but it is only significant at or near wide open throttle.

[fuzzy1]

Actually, the energy content of premium is slightly higher than regular. ...

That is odd, I usually hear the opposite.

The 2010 Prius has a high compression engine (13:1) ...

Make that an expansion ratio. Due to the Atkinson cycle, the actual compression ratio is significantly less, and variable.

[bottomfeeder]

Originally Posted by fuzzy1

That is odd, I usually hear the opposite.

Make that an expansion ratio. Due to the Atkinson cycle, the actual compression ratio is significantly less, and variable.

Energy density per unit volume tends to increase with increasing molecular weight. Regular and premium are blend dependent and, for most purposes, the same. The reality is that we are both right.

You are right about the compression ration. (Heck, I've only had this car three weeks and forgot about its Atkinson cycle.) The compression ratio is what it is, 13.0:1 in our case, but the effective compression ratio must be less.

My comments about high compression engines & premium gasoline are still correct, just not relevant to the Prius.