GAS TYPE AND LEAD ADDITIVE FOR THE M151A2

Hello Gents,


I was wondering if I should be using a LEAD additive for my 1972 M151A1? I currently use staBil fuel additive for a fuel Stabilizer ? Since this is the later model made in 72', I don't know if it was made for UNLEADED fuel at that time.



I also use the highest octane avil. Is this wrong ? Should I use the lowest ?



Need input from all the ole pros out there.



Thanks,

Jerry

je,
Since I presume your 151 does not have a catalytic converter using a lead additive will not hurt the vehicle at all. Octane is a measure of the stability of fuel not to burn before the spark plug starts the process as well as an actual chemical. The higher the octane level the more stable the fuel before burn. Heptane is what causes misfires in the engine. So, the lower the octane rating, the more heptane is in the fuel. Does this help?

Thanks for the reply.

My main issue was:

(1) I wanted to know if I was harming the valves, pistons or engine useing the high octane fuel. Since this is an older engine, I do not want to void the warrenty, hehehe. I was watching the History channel also on the octane & heptane process with gasoline.

(2) Should I be using a LEAD additive to help reduce the engine wear if anything at all ?

(3) Should I keep buring high octance unleaded fuel without the adding the LEAD additive ?

Thanks!

I would guess that the octane rating of your fuel probably won't make a lot of difference. Most MV engines were made to run on some real poor stuff, so the high octane is probably overkill, but in my experience, the higher octane fuel does burn cleaner, if that is any issue. On the lead additive, I couldn't really say if the military took unleaded gas into account when designing the Mutt. I would guess not. The only problem with running unleaded is the damage to your exhaust valves and seats. With no lead added to lubricate the valve seats, you will typically see sunken exhaust seats where they wear a little more. I have run many older engines in my Mopar muscle cars on unleaded with little or no problems. I got an occasional burnt valve, but that was from racing or really high mileage, like 150,000. If it's really bothering you, you can tear down the heads and have hardened exhaust seats installed by a machine shop and you will have no trouble. Unless you drive your Mutt a lot, I probably would not worry about it, as the engine will probably wear out other parts before the valve seats become a problem. Just my .02

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I agree with the running of the lowest possible octane fuel. I have used lead substitute, but quit it and have had no noticeable problems in farm trucks and tractors. Most military engines are made with low compression to run on low octane fuel. The higher the compression, the higher octane required. One false impression many people have is that high octane fuel gives more power because it sounds like it is something racey. The truth is, the higher the octane, the slower it burns. This is probably why the carbon build ups are noted. I, too, have put higher octane in my Dodge 440 and slowed down at the strip. It sounded dead and performed the same way. It had a compression ratio in the 8's, and liked 87 octane. We now have built a 440 with 10.5, and it wants 89 to run best without preignition ping. When refreshing military and other older heads, put hardened seats in the exhausts if they do not already have them and worry no more.

I don't know much about the 151's but as far as octane goes I know a thing or 2.
Compression ratio and spark advance determine the optimum octane for each engine, too low of an octane is bad as it will cause pre-ignition which can burn holes right through the pistons, too high and it will not burn completely leaving lots of carbon behind. It has been proven on a dyno that excessive octane will actually lower the power output of an engine.

My 87 GMC gets 10 mpg on 87 octane and 14 mpg on 92 octane :shocked:
My 70 Monte needs 94 octane to be happy.
The GPW specs calls for 68 octane minimum :shocked: Premium would probaly kill it.
The M882 /M886 will run on ok 87 but seem to run smoother on 89.
Back in the early 70's the lowest octane out there was 92

Like I said, I don't know much about 151's but I'd bet they'd run great on 86 octane :smurf: