i am just wonderin who here is runnin 89 gas in their STOCK 350 TPI's. ive run into some real bad financial problems lately so in order to save money i am tryin 89 for the first time. i searched and basically found info about just runnin the lowest octane possible without any pingin. but all i would be dependin on is the sound. if i even hear it. so anyone runnin 89 or less gas in 350 TPIs without any problems?

 

The TPI engine was designed to run on 87 octane gas. If you are still basically stock, run 87.

I have been running 87 in mine for about 7 years now, basically since I owned it..... the only thing I notice with higher octane is it runs a little smoother, and gets slightly better gas mileage, but not enough better to offset the additional cost.

 

A lot of it depends on what your base timing is set at.

 

Do you know how much should it be retarded?

 

You may want to ask the TPI guys but I think 6° to 8° is a good base allowing you to run on 89. A bit less timing and you can run 87.

 

I run 87 most of the time. 205k+ miles. No problems except horrible gas mileage (15-17).

 

gosh, i wished i got that! before the last jet change, i was getting about 8 city!

 

87 when i had my 350 with 6* timing. Now with the 383 I run 87 when its a LONG highway drive and usually 92 on the street then.

 

ya well i wish I ran 13s

 

I've heard before that gas mileage will drop if you goto a lower octane. So, be sure you keep track of you mileage if you run a lower octane. Just for comparrison...

Let assume a fill up of 14.5 gallons. (That's usually what I put in) And assume we're getting the EPA sticker gas mileage of 16mpg in city.

So we'd get 232 miles per tank.

Currently, gas is $2.12 for 87, $2.22 for 89, and $2.32 for 93. Well, it is here...I hope it's lower for yall.

So, if ya do the math running 89 will save you $1.45 and running 87 will save you $2.90 assuming you still get 16mpg.

I'm not sure if this is the correct number but, assume that you get 15 mpg when you goto 87 or 89.

So, if ya do the math running 89 will cost you $0.70 more than 93 and running 87 will save you $0.85 than running 93

I don't know that you'd really lose and entire mpg going to 87 or 89. From what ploegi said if seems you won't. But keep and eye on it and let us know how it turns out if you do.

PS - Obviously, if you're getting less MPG with the 87 or 89 then you'd have to fill up more often. For the stuff above I just assumed you put more gas in per fill up (AKA you still drove 232 miles per tank of whatever grade fuel you have in there). In reality you'd just fill up more often, putting in the same 14.5 gal per fillup, with the 87 or 89. So, it'd appear you were saving money at every fill up but you'd have to fill up more due to the lower mpg. So you'd be spending more per mile.

 

hehe

 

yup i need to keep track of what my MPG is nowadays. i wouldnt be surprised if its less. last time i checked it was about 16. may be time for a tune up.

 

personally, i don't see why the lower 87 isn't being used. i run about 9.5:1 c/r and have a carb, and run nothing but 87. the fuel injection only helps with less detonation. back the timing off and put some 87 in it. never hear of this lower mpg with lower octane deal either.

 

In my owner's manual (1987 model year) it reads:

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FUEL REQUIREMENTS

5.0 Liter (Engine Code F) and 5.7 Liter V8 Engines

Your engine is designed to operate on premium grade unleaded fuel. However, with the electronic spark control system, you may use regular unleaded fuel at slightly reduced acceleration performance.
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I too disregard this and have been using 87 octane for the past few years. I don't bother retarding the base timing. That's what the ESC is for.

I do miss the days of cheap (relatively speaking) 92 octane.

 

thanx for the replies. the 89 seems to be workin well. i havent tried 87 wit retarted timing.

right now timing is set at stock which i believe is 6*.