Run premium fuel?

EskimoPie · Aug 31, 2021

I've always used premium (91 R+M/2 in Arizona) and been happy with the performance over the past 7k miles. Just idly flipping through the manual though and I noticed it only calls for 87 knock index fuel. When I purchased, my service manager was adamant to use premium fuel. Does anybody run regular grade fuel? Any issues with it?

DOCGSS · Aug 31, 2021

I run premium. The higher octane provides protection from pre-detonation, and quality brand premium fuels have more and better detergents to clean fuel injectors and help prevent carbon buildup on valves and pitons. What premium fuel does not provide is more power, that is a common misconception.

EskimoPie · Aug 31, 2021

DOCGSS said:
I run premium. The higher octane provides protection from pre-detonation, and quality brand premium fuels have more and better detergents to clean fuel injectors and help prevent carbon buildup on valves and pitons. What premium fuel does not provide is more power, that is a common misconception.

Quality brands and additional detergents are unrelated to the octane choice as the Top Tier designation requires the detergents to be added to all grades.

While higher octane prevents detonation in high compression engines that are designed for it, in engines that are not designed for it, you don't get that benefit as you won't be getting detonation even with lower octane.

Hence the question... if our motors are designed for 87, why run premium? Does anybody here run regular consistently? Has anybody experienced knocking with 87 octane?

Ransom · Aug 31, 2021

I've only ever run regular in my Touring.

TURBO200R4 · Aug 31, 2021

EskimoPie said:
Quality brands and additional detergents are unrelated to the octane choice as the Top Tier designation requires the detergents to be added to all grades.

While higher octane prevents detonation in high compression engines that are designed for it, in engines that are not designed for it, you don't get that benefit as you won't be getting detonation even with lower octane.

Hence the question... if our motors are designed for 87, why run premium? Does anybody here run regular consistently? Has anybody experienced knocking with 87 octane?

check your manual i think the new rockets require premium

EskimoPie · Aug 31, 2021

TURBO200R4 said:
check your manual i think the new rockets require premium

Nope:

jackrotten · Aug 31, 2021

87/89 (US) is fine

TURBO200R4 · Aug 31, 2021

EskimoPie said:
Nope:

i guess regular will work.
i guess one of these days i need to study one of those manuals.

leatal · Aug 31, 2021

EskimoPie said:
Nope:

My Owner's Manual doesn't have the second paragraph but the specification pages say minimum octane of 95 RON which is 91 minimum in US. I also only use Shell premium (if possible) as it has the most cleaning detergents of all top tire fuels. Plus if you join the fuel rewards program, you save 5-10 cents per gallon.

Dr.D · Aug 31, 2021

The two paragraphs in the manual are contradictory. 95 RON grade is 91 AKI or (R+M)/2. I use top tier 91-93 and have no problems. Am I wasting money? You tell me I spent $29K for a toy.

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