| Re: [GMCnet] 455 Maintenance Specs [message #96690] |
Sat, 21 August 2010 13:23  |
Gary Casey
Messages: 448
Registered: September 2009
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Senior Member |
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Ken is certainly correct in that there are a lot of opinions on what to do - so
I feel obligate to report mine :-).
1. I can find very little correlation between engine temperature and
transmission temperature. They are mechanically connected to each other through
a very thin are remote attachment - the bell housing. In fact, one could
propose that using a hotter thermostat in the engine will reduce the
transmission temperature, not increase it. The average coolant in the radiator
has to stay at about the same temperature (heat input stays the same) so if the
hot tank gets hotter the cold tank will get colder and that means the
transmission cooler will run at a lower temperature. Not enough difference to
argue about, though.
2. I don't have much opinion about brands of oil, or about changing brands. As
an engine gets older (not age, miles) the clearances in the bearings will
gradually increase, which actually makes the minimum clearance go down. To keep
the shaft more centered a higher viscosity oil might be desirable. So I would
tend to use a higher viscosity oil, even though it will slightly reduce fuel
economy and increase oil temperature. In most was brand names of components
like filters are equivalent. My information is old, but back then Fram
developed a new paper, which allowed finer filtration. The argument was whether
it was better to filter finer or to allow more dirt to be trapped. Their
conclusion was that filters are normally replaced with very little dirt in them,
so it was better to filter finer as that would protect the engine better. Most
major manufactures build filters sold under their own name as well as for
private labels. I don't see any reason not to use any of them. And data that
I've seen shows that Fram filters are as good or better than any of the others.
Would you use a Ford (Motorcraft) filter in a Ford? Built by Fram, at least
once upon a time.
3. No comment on ZDDP. I'm told that "diesel" oil has more ZDDP, so I suppose
that would be a good thing to use. The cam/lifter interface is by now so
polished off I can't imagine it being a big deal.
4. I agree with Ken on this one.
5. As I recall, all engines built after 1970 incorporated hardened valve seats,
so were all compatible with lead-free fuel. And lead-free fuel will make the
exhaust system last twice as long. Since lead is gone, so is this argument...
6. Don't know about plugs. Most OEM passenger car plugs were, at that time,
maybe 1 heat range colder than optimum and this was to allow for the most severe
operating conditions. The GMC might be considered one of those conditions.
So what would I do? Run unleaded fuel, 15W-50 oil, Fram (or most any other) oil
filters, 200 thermostat and standard plugs gapped at .035. Just my opinion.
Gary Casey
1. I use and recommend a 180 degree thermostat. Heat is your enemy both in the
engine and the trans area. They are both bolted together and see similar heat
levels.
2. I use and highly recommend Rotella 15W40. It is a good high detergent oil.
That is all my coach has seen since new. I burn one quart of oil in 6,000
miles. You are going to get a lot of opinions on this. Rotella is available at
WalMart, AutoZone and other places. DO NOT USE FRAM filters. I like AC Delco,
WIX, and NAPA GOLD (made by Wix).
3. ZDDP levels were reduced by 1/3 several years ago. Reduced levels should
not hurt you unless you are breaking in a new engine. Adding ZDDP will not hurt
but most people do not do it.
4. 87 octane regular fuel is adequate. Octane has no bearing on the vapor
pressure of fuel. The lower octane fuels sold in higher elevations of the
country is OK if you are staying at those elevations. Stay away from ethanol
blended fuel if possible. It reduces your fuel mileage and is being blamed for
vapor lock problems. This is being primarily reported in the Western states
that just switched over to it from the previous MTBE blended stuff. In some EPA
non-attainment areas, like the whole state of Kalifornia, 10% Ethanol is all you
can buy. I live in one of those areas so I buy my GMC fuel in the next county
where I get 100% gasoline.
5. Unleaded fuel will not hurt a thing in your GMC.
6. Most people like AC Delco #7 plugs. You probably will have to order them
from your local auto parts store. They are platinum and will last 100,000
miles. Leave them gapped at .035" to .040". Leave them gapped at whatever they
are out of the box. Just check them to see that they are all the same and
somewhere between .035 and .040.
Ken B.
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