Looking for advice on which oil to use in my 2005 GMC Sierra 1500 with the 5.3 litre V8. I bought the truck 2 months ago with 140,000 miles (223,000 KM) and now need to change the engine oil. I assume that the truck was run on conventional oil by the previous owner. As I live in Edmonton Alberta and we have very cold winters, I normally use full synthetic on my other vehicles. I can buy Mobil 1 Full Synthetic High Mileage for about the same price as Castrol Edge Full Synthetic, the oil I would normally use. Is the truck ready for high mileage oil?
Full Synthetic vs HM Full Synthetic
- Thread starter SierraMan
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High mileage conventional would be best in this situation because if it was using conventional its whole life, using a synthetic could provide some additional cleaning benefits and cause hardened seals to start leaking oil as the deposits from conventional oil are cleaned away. Doesn't always happen but it might in your case with the mileage.
If you are ok with taking the risk then use the High Mileage Synthetic. I just wanted you to be aware is all.
Some folks have no issues going to a synthetic from conventional but knowing that these engines are prone to gaskets seeping oil with age I would suspect you might end up leaking some oil with a change over to synthetic (even the high mileage type), if it was conventional its whole life. Just my experiences.
These engines do just fine on conventional so no worries even in cold Alberta winters. You could always just plug it in with a timer set for 4 hours before you leave. This will warm the engine enough to help the oil flow better in the cold. But honestly I'm sure it has seen many winters with conventional and it survived just fine.
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If you switch to synthetic on a car that has been on conventional for a long time, you are asking for oil leaks. I wouldn't bother with a high mileage and just run a 5W30 in that unless it's too cold for that. If it's already leaking, then run whatever you want. That engine is not picky, my Dad ran his 2004 5.3 low enough on oil for it to knock and then drove it to Florida and back earlier this year.
OK guys, thanks for your thoughts on my question, I think I will go with the 5W30 high mileage conventional oil and use the block heater on cold days No leaks yet (touch wood) and I would like to keep it that way.
HM oils have seal conditioners, not swellers. Don't think either synthetics or HM will cause major risks.
I switched my car to high mileage synthetic at around 174k miles. I had been using conventional HM or synthetic blend HM oils for maybe 15k prior to that. A very small leak did develop 12k miles and over 2 OCI after the switch to synthetic HM, but I'm not sure if related or just a tired old camshaft seal beginning to weep.
My opinion, if no leaks and no consumption there is no reason to swithc to a HM oil, conventional or synthetic. If it ain't broke why try to fix something or believe that you can prevent something from happening by switching before you actually need it. Not like heart disease where eating right can prevent issues, a quality oil is eating right, just wait for old age to start showing up before taking medications!
IMO it doesn't really matter when you switch to HM. The seal conditioners won't affect the seals in a new engine. Whether or not it will "preserve" their sealing abilities is a matter of debate and may just be marketing hype. In fact, I'm not sure why HM exists at all. Why don't the oil companies just add their seal conditioners to the regular oil and market it for all engines, regardless of age?
I've dropped synthetic into a 10 year old jeep 4.0 with 100K miles and a 17 year old ford 5.4 with 210K miles ; no issues
Buy what 5W30 is on sale and follow the olm. Check often to ensure the sump is full and all will be well.
Last September I bought the 4Runner with 245,000 miles on it. Immediately I changed the oil to a synthertic HM oil. I don't know what oil was used for the last 17 years and I don't care.
After about six months of synthetic HM oil use in the F150, a pesky rear main oil seal seep that I had for years went away.
All my vehicles, except the Ranger, used a little oil between OCI's. With synthetic HM oil they don't. Say what you want about synthetic HM oils. I would, and do, use them in everything.
After about six months of synthetic HM oil use in the F150, a pesky rear main oil seal seep that I had for years went away.
All my vehicles, except the Ranger, used a little oil between OCI's. With synthetic HM oil they don't. Say what you want about synthetic HM oils. I would, and do, use them in everything.
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Id make the switch without an issue. Just keep an eye out for any leaks developing. I switched to Valvoline Maxlife High Mileage Synthetic Blend in my van this last oil change. It had 182k~ at the time of change, now it has over 183K on it, so its run on this oil for over 1000 miles and hasnt developed any leaks or consumption. In fact, I think it slowed any of that down, seeing as it wasnt unusual to have to add about 1/3 qt of oil to it by now when running the oil that the mechanic I was taking it to before I learned how to change my oil.
It may not be a bad idea to switch to a HM synthetic blend of some sort and run it for a OCI or two before switching to full synthetic. Ive seen this suggested on a couple other sites. I think their rational was it would alert you to any leaks developing without it getting as bad as it would be on a full synthetic. If the logic behind this is flawed, let me know. But it seems to be fairly solid advice to me.
It may not be a bad idea to switch to a HM synthetic blend of some sort and run it for a OCI or two before switching to full synthetic. Ive seen this suggested on a couple other sites. I think their rational was it would alert you to any leaks developing without it getting as bad as it would be on a full synthetic. If the logic behind this is flawed, let me know. But it seems to be fairly solid advice to me.
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