Do you guys feel that Sunoco's Ultra 94 is better than other 91 octane fuel from other stations for a 4.5/4.9 engine?

Not without advancing the timing a couple of degrees!

I like just Shell 93'. Something about the additives (or something) just make my car feel peppier. That was before I advanced the timing, now it really does but I have not tried any other gases in it since, though. No one around my area sells anything over 93'.

Your lucky to get 93 ... The best I can do in California is 91.

Eh Sunoco doesn't sell the 94 south of the border?

No difference unless your timing is advanced and you hear spark knock. Could even get less power (you ideally want the lowest octane for which you don't hear spark knock).

I use Shell 93 in my 1991 4.9L. Shell is the only gasoline to meet Top Tier standards that GM, BMW, and Toyota developed jointly. Good enough for me.

Recently bought for $250 via a bank bid,a repo 92 Eldo with 169K miles and I've been running BP 87 octane with Lucas Oil gas additive for top cylinder and injector cleaning and no apparent spark knock with this combo .Lucas claims with this additive no need for higher octane fuel . Decrease in 87 octane 20 cent fuel price compared to premium per tankful affords $3.00 additive price that I KNOW is in the tank! Pulled the previous owners worn AC plugs after one tank and they were burning clean with light beige -tan color. Currently using Bosch Platinum 4 sparkplugs with average 25mpg fuel economy with a new K&N stock airfilter.

Lucas works by getting air into the oil and making it foam up, that's how it coats parts better and lubricates much worse in the long run. Not sure what that would do in the gas tank, but I wouldn't trust it...

Bosch platinum +4 plugs shroud the spark. Your best bet, especially with these cars, is to stay with AC Delco, particularly with spark plugs.

K&N filters do offer a bit less resistance, but these cars have MAP sensors and will adjust the fuel with respect to the air, so you're not really going to get much out of that. If you're autocrossing the car or something where pieces of seconds count, indulge yourself. Otherwise, it's not really necessary.

I don't think I'd bother with 94... I've seen it around, sure... But I don't like the idea of not having access to it everywhere. Wouldn't want to get used to it, take a road trip and find out I need to retard my timing to get out of Ohio...anyone got a wrench? :thepan:

Believe it or not I have had zero problems in my 86 Deville 4100 running 87 octane for years like my owner's manual says is required. No sounds and no noticeable difference whatsoever to me between 87 and 93 in my normal daily driving. I do, however, stay away from non-brand-name gas and go to stations that get good traffic flow for fresher gas supply. I also put in a bottle of fuel additive every couple of months for good meaure...usually Chevron Techron brand or STP. I guess the later versions of the 4.x engine had more need for a high octane?

Me...I run regular and get the same gas mileage as my mother's 6 cyl. 2000 Acura RL (which requires/recommends premium gas).

I think with the 2000 vehicle, it should have knock sensors. Don't get me wrong, I know jack sugar about Acuras... But the technology was readily available by then, so if it has them, it should just be getting the best bang it can out of whatever octane you put in there.

I personally noticed my 90 Fleetwood runs ok on 89, but seemed like it got slightly worse mileage. I'm not positive, mind you. I don't have extra cash to be blowing on mileage controlled experiments lol.

Careful with fuel additives. Some of them can gum up a cat, and many of them are not fuel-injector friendly. STP paid like the biggest fine for false advertising in history...so might want to keep an eye on them :suspect:

Lucas works by getting air into the oil and making it foam up, that's how it coats parts better and lubricates much worse in the long run. Not sure what that would do in the gas tank, but I wouldn't trust it...


I think he was talking about Lucas fuel system treatment....totally different stuff! They make more than just engine oil additives! :cookoo:

Well I hope the experts here will correct me, but if you are using the appropriate premium unleaded fuel, you have all of the additive you need. No additivies need apply. I have learned this through countless cars. Don't mess with addy's. If your fuel filter is plugged, change it. If you have a plugged injector, have a shop clean it/replace it. Don't dump your money into useless chemicals that won't do a damned thing for your fuel system. This isn't the 70's any more.