What octane fuel do you use?

87... after almost 12K, no pinging ever.

 

I've had pinging issues with 87 octane in warm weather and heavy load (due to terrain here). So it gets atleast 89, gets 93 if im going to be racing in hot weather (no, not because I think the 93 will make it faster). Detonation is an issue with these cars if driven hard under certain conditions.

 

Well, 95 RON (UK - we measure it differently I think) for about 42k miles..
But, as a test, my last tank was 97 RON - made no difference( apart from the cost!)
87 "octane" in the US is around 92 RON.

 

87...but i stick to brandname gas (chevron & shell).

 

On the first edition of the owners manual 88 was required. After a few months of production it was changed to 87. At the begining I was using 89. Now I use 87 and have not noticed pinging or a decrease in MPG. We will never know if 88 was a typo or if indeed the engine optimal performance is achieved with 88.

 

As stated in many other threads. The 88 was a typo. 87 is fine, there is no need for 89 or 93 octane. And personally I found that there is a difference between generic brand and name brand. I dont use generic anymore.

 

87 no problems.

 

yeppers. 87 no problems. however, on a long trip, 89 will net you a better mpg and return. especially when you have to drive 80+ to keep up with flowing traffic.

 

This agrees with the hill climb data:

Sorry, the plateau line is 87 octane on the hill climb. In contrast, the 89 octane fuel continues to provide power up the hill. The scale on the left is the amount of fuel burned going up the hill. What happens is 89 octane allows the ICE to continue providing power up the hill and avoid having to draw on traction battery energy to continue the hill climb. But notice how at 80 mph, the two curves nearly intersect.

What this means is the fuel consumed as a function of load are about equal at 80 mph on the 8% grade (lightly loaded Prius.) At higher power settings, the Prius tunes for the higher octane and the fuel efficiency FROM THE ICE is improved over 87 octane.

At lower speeds or power settings, a quality 87 octane works best. But if you're planning to cruise at high speeds with significant hills, 89 octane would be a better choice because it lets the ICE run efficiently at high power settings and avoids the battery charge-discharge tax.

Bob Wilson

 

87 Octane and no pinging here in Texas where the temps are running mid to high 90s consistently now. I only use Exxon fuel in my Prius.

 

Yeah, I'm paranoid and suspicious but given the amount of time it took Toyota to come out and confirm the grade of gas they recomended, I've always been suspicious that the "new" beltless engine does actually run better on a higher grade, but Toyota was afraid to admit it. ( The Insight runs on 87 octane, and older Prius run on 87 octane, if it would of come out that the New Prius suddenly required a higher octane? I think it would of been bad PR for Prius.)

No proof, nothing to support this suspicion...but it took them forever to finally come out and say 87 (or better) octane...

 

I have a couple of newbie engineering questions:

Out of all the carbon chain molecules from methane to ethane to pentane to decane and up, why is octane the only one we care about in gasoline formulations?

Bob, on your famous chart, I can't tell how you conclude that at low speeds 87 works best and at high speeds with hills 89 is best. It's probably my fault for not being able to read the thing. I can't tell which lines are 87 and which 89 octane, and I can't tell where the crossing points would be in speed and hilliness where one works better than the other. If you could explain these things, it would help a lot of us.

 

Great questions, kgall.

May I just add here, as an aside, that one of the little-appreciated benefits of electric drive is that you have NONE of this confusion? Name brand electricity? Nope. Higher octane? Nope. Detergent package? Nope. Leaking on your shoes? Nope. Breathing benzene during fillup? Nope.

Sorry. Couldn't help myself, as usual.

 

With respect to the often discussed 88 octane typographic error in the 2010 Prius manual, it amuses me that people see a conspiracy. Among others, there are two main reasons to assume that this was nothing more than a typo:

1) Toyota categorically stated that the manual was in error, and the real fuel requirement was 87 octane.

2) 88 octane is not a standard octane for the North American market. If Toyota actually intended the engine to run on premium fuel, they would have stated a standard premium fuel octane.

Tom

 

I love it when people talk dirty to me

Jayman
B.Sc Chemical Engineering

With my FJ, it states in the owner manual and on the fuel filler door to use Premium only. Toyota soon issued a TSB stating that regular was fine, the Premium was to achieve the rated HP and torque

Since I only put around 2,500 miles a year on my FJ, I'll keep using premium. Since the Shell V Power contains no ethanol, my FJ honestly does gain a couple of mpg running it

 

The Octane rating is the percentage of iso-Octane in a mixture of iso-Octane and Heptane with the same resistance to detonation as the gasoline being measured. Actual gas is a more complicated mix, or else no gas could have an Octane rating of over 100.

 

I added some details but it comes down to this:

• 87 octane - higher energy per unit but power limited. At higher power settings, the car has to derate the ICE power and use traction battery charge-discharge to provide the extra power. There is no 'free lunch' and passing power through the battery charge-discharge is not as efficient as running straight from ICE.
• 89 octane - lower energy per unit but at higher power settings, the engine can self-tune to use a more efficient compression ratio. The BSFC improves over what 87 octane can achieve due to the higher compression ratio.

Side note, if the 1.8L engine had the ability to adjust the intake valve duration as well as angle, it could eliminate the throttle plate and extend the efficient power band even further. Higher octane fuels would still provide more efficiency at high power settings. However, the lower power settings could use the ICE a little more instead of ICE/hybrid mode cycling. Probably of marginal benefit except to thermodynamic nit-pickers. Still it could be a significant boost to all non-hybrid, ICE-only vehicles ... significant improvement.

Bob Wilson

 

I am still amused at how many people believe that high octane fuel has "more power" than regular.