The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.
__________________ Firefighter/Paramedic Local 1555
1989 Wrangler 5.5" Lift 33"s - SOLD
1997 Wrangler 6" Lift 35"s - SOLD
2008 Wrangler 2.5" Lift 35"s - SOLD
I have always ran the cheapest crap I could find but I am really reconsidering that. Cheaper gas usually causes gunk buildup in your engine which is not good. Other than that, I might switch to better and more expensive gas due to the reaction my backup vehicle has to that. Cheap low Octane gas I usually get less response to the pedal, worse gas mileage and a check engine light that come on periodically. With Shell high Octane premium I am getting much better pedal response, better gas mileage and no more check engine light. I guess all these gauges in newer vehicle are good for something
I wonder if the gunk buildup is what leads to blow-by that has killed high mileage engines in the past? It could be worth the extra $ at the pump if it keeps you from replacement or rebuilding the engine in the future.
Female rolling with the 93 YJ SOA Locked and Hard at Play
haven't noticed a difference, and definitely tested all three octane levels available. when prices were lower, it seemed a worthwhile hedge to buy the high just in case it helped, but given no real tangible difference and prices, i think the regular is fine
If it does improve your gas mileage is it enough to be worth the extra price?
it depends on the difference in price from reg to mid-grade to premium. Here in Jersey, the difference between reg and premium is about $0.20; at that much of a difference, its like paying $0.05 more for regular.
In my opinion, its well worth it.
NJ Army National Guard
Ready for deployment.
So many mods planned for the upcoming YJ:
3.5" lift kit
33" General Grabbers
Massey Ferguason Grey body
Kubota Orange suspension components