Trends in "penalty" for using premium gas?

**elagache** · 12-09-2010, 07:35 PM

Dear Team Buick community,

I'm caring for a "family heirloom" 1965 Buick Special wagon that has a long history with many ups and downs. One arguable down came in 1979 when my Dad had the engine rebuilt. Since we had been really hurt by the OPEC oil embargo, my Dad decided to have the engine downgraded from a high-compression 300 V8 to the standard compression.

Since the engine was hobbled because the extra cost of premium gas and it is time to rebuild the engine, I wondered if it was still such a burden to have a car running on premium. I suppose few folks on this forum would admit to such petty ecomonic concerns, but then - you still have to pay for the darn gas when you get to the pump!!

Out of curiosity, I downloaded some data from the U.S. Energy Information Administration http://www.eia.doe.gov/, did some simple spreadsheet manipulations and compared out much it cost fill up with premium gas instead of regular. The results were a bit surprising. There is 15 years of data at that government website. Over that time the difference in price for premium has remained the same about 20 cents a gallon. However, as we all know, the overall price of gas has . . . skyrocketed! As a result, the "penality" you pay for filling up with premium has actually declined. In 1995, you had to pay 15% more to fill up with premium. Today it is only 7%!

To me that's just another reason to restore my venerable 300 V8 to high compression, but it might make some of you less leary to fill up your high-performance Buick!

Am I the last person to figure this out? If so, is there a well composed web site that explains this trend? I slapped the numbers together so that I could argue with folks, but it would help me to have some reference I could point to.

Happy Motoring,

Edouard in Orinda, CA

**Houndogforever** · 12-09-2010, 08:48 PM

Most of these 30-50 year old cars are driven for pleasure, nice days and only for having fun. How many miles do you put on this car, 3000 a year? Most, not all, of these fine old cars are not your day to day driver to get to work and back.

**Bob** · 12-10-2010, 08:03 AM

You are probably right! And I agree with Houndog... When I drive my classic performance car I look for the premium pump

**elagache** · 12-10-2010, 08:28 AM

Dear Bob and Houndogforever,

I certainly agree with both of you!

I'm in a odd position of having to decide if I should "undo the damage" to bring my engine back up to high-compression. Like everyone else, the car isn't going to get a lot miles (thus fuel costs aren't a big issue.) Still, knowing the "premium penalty" is decreasing is just one more reason for me to follow my heart and restore the engine to its factory condition.

For everyone else, hey it means you can "fill'er up" with less guilt!

Ya'know, it might even encourage classic car folks to drive a little more - road trip anybody?

Cheers, Edouard

**Airy Cat** · 12-10-2010, 07:49 PM

I run premium fuel in all of my older Buicks. In California premium is only 91 octane which was regular fuel back in the 50s. A friend of mine ran regular in his '56 Special and he burned a hole through one of the pistons. In my '65 Wildcat I run a 50/50 mixture of 100LL Av gas and 91 octane pump gas and it really livens up that 401. I've been doing that for 15 years with no problems!

**elagache** · 12-11-2010, 09:58 AM

Dear Team Buick members,

Airy Cat is revealing more of my naivete. I didn't know that gasoline octane as suffered the same fate as "one pound can" of coffee (now down to 3/4 of a pound and still declining).

Can somebody tell me what was the octane rating around 1965 when my car was built? Of course I could look this up in the car's service manual . . . . that is sitting on the passenger seat while the car languishes in the body shop . . . . *sigh*

Thanks for all the interesting vignettes

Cheers, Edouard

**Airy Cat** · 12-11-2010, 10:30 PM

Back in 1965 premium octane rating was around 100 to 104.
If I were you I wouldn't use that 87 octane crap in anything!

**39CENT** · 12-11-2010, 10:45 PM

just to put my nose into this, Mentioning costs I have posted several times about gasoline 'cost' relative to todays relative income, but havnt had any comments. I think that todays gas is comparatively close to the 60,s. era gas price.

**wireb** · 12-12-2010, 09:16 AM

Just curious what goes into converting from the low to high compression on a 300? I have the 2 barrel intake (assuming the low compression) 1967 (based on casting numbers. Unfortunately the the build numbers were machined off when the PO had it rebuilt.) Thought about getting those extra 50 ponies and can track down a intake. But never looked into the process to change the compression ratio.

Another side note is there any way to check / measure the compression ratio on a stand? I can tell the engine was rebuilt at some point but no idea exactly what was done. Would be nice if it was already swapped to the higher ratio and I just need to go locate a intake

**alleycat** · 12-12-2010, 10:29 AM

I'm going to throw in my 2-bits here as well! The gasoline that we have now and the gasoline we use to have back in the 60's is completely different stuff. The gas back in the 60's, both regular and premium, was full of tetraethel lead, and not much else. The gas was "hotter" than a 2-dollar pistol! It took practly no spark at all to set it off! It made great parts cleaning solvent. Try that with todays gas, all you'll get is a mess of goo. The stuff is different. I've built a lot of serious "pushin the edge" engines, and about 15 years ago I started thinking that, at least, I, am building engines incorrectly. If you are useing "race" gas, which is basicly old school 100-104 premium, then the old rules still apply. But, if you are buying gas at the corner gas mart, then something different is required. I started thinking that perhaps some of those old high comp engines that Buick, Cad, Olds, turned out, may be closer to what would work, than anybody thinks! These engines got a bad rap through the 80's when gas got REALLY bad.

I have a 72 chev p-up, full boat rig. The engine was getting to the point of needing a freshin-up. It's got a 402 big block in it. I'm not particulary impressed with chevys big block. It strikes me as neither fish nor fowl. It does not do anything really good, or anything really bad, perfect candidate to see what I can get out of it with the gas that 99.9% all of us use. I took no prisoners on this build, every trick I knew of, could come up with, etc...5 "builds" later I am getting close to answers.

I don't have "new" cars. My wife has a newish Exploder. I drive my old cars. They need to work in todays world. I dislike the price of gas, and I REALLY hate 12 odd or less mpg! Mpg will also tell you just how good or not a engine is working. So, everything I learned with my BB chev I will apply to my Buicks and others I have.

My truck is a square brick, it weighs about 5000 lbs, the engine is a 427 (stroked crank), it gets right at 20 mpg. It's kicking out about 400 hp and about 500 ft lbs of torque, all at about 2000 rpm. This is very good. Most big engine build ups in the car mags, the dyno pull does'ent even start untill 3000-3500 rpm. And, I can get more! So! This is what I found.
Compression is good. It makes torque. Todays gas is more like deisel than gas. Up the comp and adjust the spark to avoid preignition/detonation. Polish the piston/chamber/valves, no sharp edges! MSD 6 ignition. Valve/valve pocket p&p, dynamic compression is probably more important than static comp, a roller cam is a really good idea as well. alleycat