New owner here. I was dismayed at the first fill up to notice the premium sticker, so I went with it.
But I want to know if anyone has done much research or has much experience in not using it. I mean, this engine does NOT make that much power out of 4 liters, so what on earth is it doing with premium??
What is the compression ratio?
I'm in denver and actually higher up usually, so I know I can at least downgrade to midgrade safely, but I'd love to hear any real world experience with this pig of an engine.
Thanks!

 

With gas prices this low who cares I remember a couple years ago it was like $90 to fill the rover... Not the case anymore!

Sorry I can't add any actual good info. as to why...

 

Most here will tell you that premium is a must. One of the reasons is that these engines are oversquare or short-stroke engines.

 

Just do it.

The reason is the computer retards the timing to prevent predetonation when it senses low grade fuel.

It will run but you will get less mpg and (even) less power while not being as smooth.

Also it's a good idea to go name brand top tier for the extra detergent package it contains.

I've seen the inside of my engine and fuel rail before and after quality fuel (i used cheaper ARCO (BP) premium for a while... You don't want to do that to your engine.

I was in the shop for fuel injector issues (yes, related) and my mechanic pulled me aside and scolded me for using cheap gas.

Now that I've run nothing but Chevron premium for several years I can tell instantly when I get a tank of inferior gas... and yes it does vary, some stations being of better quality with the same brand than others.

 

There is also the fact that higher octane fuels burn cooler than lower octane fuel. The hotter the operating temperature, the greater chance for sludge formation. That reason, combined with the better gas mileage when running premium reminds me to got go cheap at the pump.

 

Yes you can really tell a difference with premium. I had a issues with the truck having what to most would sound like a knock when I first got my truck. Searched for stuck lifters, slipped sleeves and low oil pressure. Everything was fine internally with the engine. I switched to only using shell 93 in the truck and within two tanks the noise was gone and I saw myself getting better gas mileage. Now after a year of only shell fuel I can instantly tell if my wife stops somewhere else, she does't like spend the time to go out of the way to get shell fuel.

 

all in the set up. these things run better on premium. programmed and built that way. I have a pick up that seems to run better on e85, than premium. I just filled up for like $30. not as fun as driving the disco.......... it is what it is....enjoy it.

 

Yeah, I'm enjoying it now while I can.....

CR is what, 9.35:1? IIRC that's what's stamped on my block/heads....so primo it is. Also....with how fragile these engines seem to be, I'd rather use the good stuff....even if it's basically pouring it out of the tail pipe.

 

I've been alternating between 89 & 91 every 2 or 3 fillups. Haven't had any issues in several years.

 

It is really down to compression ratio and ignition advance. It also depends on the consistency and quality of standard grade petrol in and around the US. If in doubt use premium but good quality standard SHOULD suffice.

In europe and the UK I have never used premium except for high compression and high performance engines, it is designed ideally for the Ferarris, Porches and the like not for Fords and GM's.

Premium does run better and cooler in most cases and avoids pre-detonation/pre-ignition if the standard fuel is crap but if premium isn't readily available standard fuel won't harm the engine providing it isn't total rubbish. Verified octane rating is the king of all petrol fuels.

In all of my diesels I always run the standard gazole crap and none of this fancy sweet smelling or additive rubbish.

I can't advise on the US fuel market but this is a guide to the UK market.

Types of Car Fuel - Including Diesel, Petrol, LPG and Biodiesel