| 455 Maintenance Specs [message #96559] |
Fri, 20 August 2010 16:24  |
Benny Hill
Messages: 18
Registered: August 2010
Karma: 0
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Junior Member |
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Greetings fellow GMCer's,
I am brand new to owning a GMC, the finest motorhome ever made in my opinion. I have a few questions to ask regarding my 455 engine.
Was it originally designed to run on leaded fuel back in 1976 and if so should I be adding lead additive when I fuel up?
What fuel grade is recommended driving here in the Florida heat?
Should I be installing the original spec AC spark plugs or is there a better AC plug number to be using with the new fuels?
I read that some of you are running Mobil-1 15w-50. That is a heavier weight than recommended in the Owner's Manual. Any concerns of it being too heavy on cold engine start up?
Can anyone recommend a good over the counter ZDDP additive to use with non-synthetic grade oil if I choose to go that route?
Can I use a 180 Degree Thermostat or will this cause the engine to run too cold or make the stock clutch fan cycle other than normal? I have no overheating problems that I know of, but am concerned about the engine running on the hot side here in Florida with a 195 thermostat.
Thanks for any guidance you can provide. I am excited about owning my GMC and can’t wait to get going on tuning it up. I thought I should ask the experts first before making any novice mistakes.
Benny Hill
Shopping for a GMC
Florida
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| Re: 455 Maintenance Specs [message #96563 is a reply to message #96559] |
Fri, 20 August 2010 16:51  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Benny Hill wrote on Fri, 20 August 2010 16:24 |
Greetings fellow GMCer's,
I am brand new to owning a GMC, the finest motorhome ever made in my opinion. I have a few questions to ask regarding my 455 engine.
Was it originally designed to run on leaded fuel back in 1976 and if so should I be adding lead additive when I fuel up?
What fuel grade is recommended driving here in the Florida heat?
Should I be installing the original spec AC spark plugs or is there a better AC plug number to be using with the new fuels?
I read that some of you are running Mobil-1 15w-50. That is a heavier weight than recommended in the Owner's Manual. Any concerns of it being too heavy on cold engine start up?
Can anyone recommend a good over the counter ZDDP additive to use with non-synthetic grade oil if I choose to go that route?
Can I use a 180 Degree Thermostat or will this cause the engine to run too cold or make the stock clutch fan cycle other than normal? I have no overheating problems that I know of, but am concerned about the engine running on the hot side here in Florida with a 195 thermostat.
Thanks for any guidance you can provide. I am excited about owning my GMC and can’t wait to get going on tuning it up. I thought I should ask the experts first before making any novice mistakes.
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You are going to get answers (opinions) all over the place on your questions. Be prepared for this and select the ones you feel are correct or that apply to you.
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.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: 455 Maintenance Specs [message #96576 is a reply to message #96559] |
Fri, 20 August 2010 18:09 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| Benny Hill wrote on Fri, 20 August 2010 17:24 |
Greetings fellow GMCer's,
I am brand new to owning a GMC, the finest motorhome ever made in my opinion. I have a few questions to ask regarding my 455 engine.
Was it originally designed to run on leaded fuel back in 1976 and if so should I be adding lead additive when I fuel up?
What fuel grade is recommended driving here in the Florida heat?
Should I be installing the original spec AC spark plugs or is there a better AC plug number to be using with the new fuels?
I read that some of you are running Mobil-1 15w-50. That is a heavier weight than recommended in the Owner's Manual. Any concerns of it being too heavy on cold engine start up?
Can anyone recommend a good over the counter ZDDP additive to use with non-synthetic grade oil if I choose to go that route?
Can I use a 180 Degree Thermostat or will this cause the engine to run too cold or make the stock clutch fan cycle other than normal? I have no overheating problems that I know of, but am concerned about the engine running on the hot side here in Florida with a 195 thermostat.
Thanks for any guidance you can provide. I am excited about owning my GMC and can’t wait to get going on tuning it up. I thought I should ask the experts first before making any novice mistakes.
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Benny,
Ken gave you a very good and complete set of answers, but he left out one....
The 15-50 oil will not be too heavy ever. The weight (viscosity) of the recommended oils is based on data that is very old. The other neat thing is that many of the 15-50 family have the high levels of anti-wear additive that has been banned from common passcar street engines.
Next, Welcome to the cult, brotherhood or asylum.
It is good that you are starting out planning to take good care of your coach. Coaches are a lot like boats (the only real difference is that water can leak out of a coach). And one thing well understood in that world is that watermen and their boats - they take care of each other.
And as I am want to say to all new owners, it is a paraphrase of a waterman's greeting to a new vessel.
May the Good Lord bless this coach and all those that set forth within her.
Welcome
Matt Colie
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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