What Octane Grade Fuel for 3800 SC?

yes, it's the same way. GTPs should run on super.

I think they lowered the requirement in '04 but the timing tables didn't really change too much. They are just counting more on the 'bad fuel' timing table and knock sensor. I don't agree with the decision, I think they'll just run into more engines that need head gaskets replaced and crappy performance.

i'm sure the genV blower helps reduce the need for 93, but i would still run it if i had a 04+ GTP

The GenV GTPs were rated at 260HP, but because of the PCM programming, they were no faster than the 240HP version.

Story last week in KC Star says that (at least in MO) that E10 regular gas has an octane rating of 89.3 which is THE SAME as medium grade gas. But most stations still charge $.10/gallon more for medium grade. I've been putting mid-grade in for awhile now. I know the manual says premium, but my wallet says 'HUH?" Car runs fine, ECU slows timing to adjust for lower octane anyway.

SO, I'm going to fill up with regular today and run on that for awhile.

State law says you only need to post the MINIMUM octane rating, not the actual rating. 87 in the min here, but it's really almost 90... Damn oil company f_ckers!

I've been running regular in my Riv for over 2 years. It seems to be fine except for other issues that are wrong with it. The price of 87 octane right now i about $3.70 a gallon where I live, NYC/lower Westchester. Premium fuel is close to 4 bucks now. Diesel was 4.71 a gallon last night. So I won't be putting anything over 87 in my car anytime soon.

wow in central NY 87 was 3.27 yesterday i think

Today I have 3.39 and 3.69 for 89 and 91. It's getting harder and harder to schedule in my belts swap, been w/o the SC belt for a couple months.

Dave's got a good idea having the SC belt off. If you guys are running 87, you should do the same. This is the only way to ensure the engine is safe from knocking under load.

You can use 89 or even 87 if you are very careful to accelerate very slowly, and only drive on the freeway, but this is not considered normal driving. To get the spec performance of 240hp, you need to use premium. Otherwise, when you hit full throttle... listen closely and you'll hear "Clack-cla-clink-clink". This is engine knock, which is bad.

Maybe you've been driving on 87 for so long that the PCM has gotten tired of retarding timing, so it switched over to the "bad gas" timing tables, in which case your engine may be safe(r), but your car is now just slow. To me, doing this is like driving a vehicle with the donut spare for months at a time.

How much do you really save on a fill up by using 87. $1.50? $2.00 maybe?

Quote :

How much do you really save on a fill up by using 87. $1.50? $2.00 maybe?

It's about $3.00 and some change, but still.. that's so miniscule, hardly worth frying your engine over.

especially considering you get measurably worse mileage with regular

Well when you think about it, the difference between 87 and 93 in price ranges anywhere between 20 to 25 cents a gallon. Saying it's a $.20 difference, thats 4 bucks saved every fill up on 20 gallons of fuel, thats 16 a month, and $192 saved per year on fuel. So it does add up. That money saved can cover other issues, or minor repairs needed, an inspection and tune up...etc.

Edit: and the prices went up again, it is now around $3.80 for regular, a $.10 increase in what 2 days

Now take into account like Jason said the miles that you're losing, and you're probably not much further ahead of the saving game. Now tack on the damage you're doing to your engine over that year.

I can only dream of buying 94/93/92... unless I want to pay $7 for 100 unleaded race gas. High octane around here is 91 these days.

Dave - maybe that's the reason for some of your KR? I'm sure you've thought of this though...

Oh I'm sure running 93/94 would make some difference, but it's not an option, unless I want to pay thru the nose to mix 100 race gas with the 91. Not gonna happen. I rarely go WOT on the street, or even remotely close to it. I can live with 3-4 deg of KR on the occasional hard acceleration, doubt it will do any damage. If I get my PT figured out one of these days, I may back the timing off a couple degrees from the DHP settings. For the time being, I'm more concerned with taking it a bit easier on the street instead of gulping gas with a heavy right foot.

BTW, in most places where higher octane gas is not offered, it is because of the area's elevation. I go out to the Black Hills of SD every couple years or so, and all they have at most stations is 87 or 89.

I always wondered - what does elevation have to do with the octane level sold in that area?

From Wiki:

Regional variations
Octane ratings can vary greatly from region to region. For example, the minimum octane rating available in much of the United States is 87 AKI and the highest is 93. However this does not mean that the gas is different.

In the Rocky Mountain (high altitude) states, 85 octane is the minimum octane and 91 is the maximum octane available in fuel. The reason for this is that in higher-altitude areas, a typical combustion engine draws in less air per cycle due to the reduced density of the atmosphere. This directly translates to reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill up a car with a carburetor that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains, but at sea level the fuel may cause damage to the engine. A disadvantage to this strategy is that most turbocharged vehicles are unable to produce full power, even when using the "premium" 91 AKI fuel. In some east coast states, up to 94 AKI is available [5]. In parts of the Midwest (primarily Minnesota, Illinois and Missouri) ethanol based E-85 fuel with 105 AKI is available [6].

Another reason HERE, could simply be demand. Maybe this region has a low percentage of owners of cars with Premium requirements, actually buying premium as they should be. If stations aren't selling it, they won't offer it. I used to be able to buy 92 for my 68 a couple years ago at a few stations close to me. Nothing higher than 91 now. Even last summer I had a station not too far out of my way that still had 92, but not anymore.

no, it's completely related to elevation. Sea level 87/89/92-93. higher elevs 85/87/89. The higher your altitude the lower the air density.

Some regions only have 91 for emissions purposes instead of 92-93-94.

When I was in Ohio at Salem, Quaker City Raceway, elevation about 1000, I found plenty of 93/94. Fargo elevation is only 899. So we're a bit lower, have no real emissions requirements, no testing, but I can't buy 92. Explain that. I attribute it to lack of demand.

Regarding Premium - even though gas prices are skyrocketing, the difference between octanes is still only 20 cents more.

Good thing THOSE figures didn't go up. Imagine regular being 4.00 and premium being 4.50 or something. Now that would suck.

In Fargo these days, the diff between 87 and 91 is usually 30 cents now. Used to be around 20-25 a couple years ago.

Gas is crazy nowadays, is there any mixture i can use instead of premium every time?

In your cosworth vega ?
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