oil help - I have 99 2500 hd 6.0. 140000 mi want to change over to full synthetic. Want your opinions please good or bad. Also what brand i usally ...

I have 99 2500 hd 6.0. 140000 mi want to change over to full synthetic. Want your opinions please good or bad. Also what brand i usally mobile one or Valvoline.

With that many miles on your truck I would stick with the regular oil. In many cases, switching conventional oil to full synthetic on a high-mileage vehicle can have detrimental effects on the engine. Synthetics have a thinner viscosity and could easily damage gaskets and other delicate parts of your engine when transitioning from conventional oil, which has a thicker viscosity.

There will be lots of opinions on this subject.It is my understanding that there are no detrimental effects when switching from conventional to synthetic oil no matter how many miles you have on your truck.The benefits of synthetic oils are longer oil change intervals and better cold starts.Some more expensive brands may have a better additive package as well.I use full synthetic oil in all my vehicles and change oil/filter every 5000 miles.It may be possible to go longer if the vehicle sees light duty.You can get Mobil1 farly cheap at Wally World or Costco.

That's why i started this topic is to get everyone's view. When out today and bought full synthetic for the truck and duel blend for the Tahoe. I will see if i can tell the difference.

I have heard that synthetic oil can leak through areas where conventional cannot. The molecules are actually alot smaller. That being said, I switched my old RSX to synthetic at 150k and had no problems, and those motors are basically 0 tolerance/interference fit. IMHO Synthetic oil is better in general, however if conventional got you 140k+ why switch now? Just put some high mileage name brand in it and roll.

I have used only Castrol GTX oil in my vehicles over the last 30+ years. Never had an engine problem with any of them, but I don't beat on my equipment either. I've run a diesel for about 10 years on Mobil1 Delvac synthetic with good results too.

When it comes time for an oil change in my Sierra 5.3 (recently bought with 9000 miles on it), I plan to put Mobil1 in it.

There is lots of misinformation and myths about synthetic oils.

The molecules are not smaller, they are all all the same size, its just that non-synthetic oils have molecules of varying sizes. Molecules all the same size mean less friction and less heat.

Synthetic oils do not necessarily have thinner viscosities then identical mineral oil . Oil viscosity of engine oil has to fall into a range, so all oils labeled 5W-30 all fall into the same range.

Leaks occur because of defective seals and almost always exist prior to using synthetic oil.

My CTS came with synthetic oil and requires synthetic oil. Putting non-synthetic oil could cause engine damage so say the owners manual.

PS-I have been using synthetic oil for a very long time.

Should you put synthetic oil in an engine over 100,000 running on mineral oil? You can if the engine is in very good mechanical condition. Synthetic oil is not going to cure problems. But you have to weigh the cost effectiveness of doing so.

My truck is due for a oil change and I'm going sythetic. The first time I ran syth. was with my 97'blazer and I was told since I was goin to use it I should run a half blend then on the second run through I could use full sythetic

Like I said, lots of myths about synthetic oil.

Remember though, like tires and beer, not all synthetic oils are created equal. With oil the old saying is true, you get what you pay for. If its cheap, its cheap for a reason as they likely to have cut corners to be able to sell it at that price. Also avoid generic/store brand synthetic oils unless you like taking chances. Recent industry random testing has found many store brands to be not as labeled, in other words a crap shoot as to what you really are getting inside the bottle.

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