Why must I run premium gas to avoid engine noise??

[Scott Hawn]

My engine sounds terrible under load on anything but 93 octane. It did not do this from new. It started at about 17,000miles I now have 20,000 on it. I know it calls for 87 octane in the manual. Is there something wrong ? Can the dealer do anything about it or am I just stuck with running expensive gas ?

[KLS]

Something must be wrong with the engine controls. This is a warranty item.


Ken

[toyoman_4ever]

try different brand fuel

[KLS]

Originally posted by toyoman_4ever
try different brand fuel

Trying different fuel may make a difference in engine performance, but a modern computer controlled engine should never ping or have ignition knock, just run better or worse depending on the quality of the fuel. It's the job of the knock sensor and related components to prevent that knock.


Ken

[v8Toilet]

Those knock sensors aren’t fool proof. The owner’s manual says 87 or higher, which means you can get away with 87 but for best performance this engine really needs at least 91.

My engine does monetarily ping with 87 in hot weather and it gets .5 mpg better on average with 93. With the way gas prices are now though @ $1.80 for 93 it costs me $4 more to fill my tank with 93 so I fill it with 87 now. 89 octane is just a blend of 87 and 93 and is really a waste of your money. The gas stations also make the most money on 89 grade.

If you do some upgrades like headers intake and exhaust your engine might become more octane tolerant and do fine on 87. Some people will argue though that those modifications aren’t cost effective and they are probably right but then again so isn’t buying a new car every fours years or even buying a pickup truck.

[sdmahr]

My truck has never seen anything other than 87 octane, and of all different varieties. I cannot recall the engine ever "pinging" or spark-knocking. I have pulled a camper and boat as well without any noises.

I agree with Ken, take it in to get it checked out.