Engine oil type?

2002 CHEVROLET SILVERADO
120,000 MILES • V8 • 4WD • AUTOMATIC
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ROBERT KIRSCHNER
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I have heard that you should never switch to a synthetic oil if the motor has been broken in, and has used a conventional oil for several years. Is this true. My next question is my truck, 2002 4x4 Z-71 chevy silverado...5.3 V-8 automatic, has been running 10w40 valvaline for years. it was purchased from my father in law. I was wondering if castrol high mileage 5w30 would be a wise switch, but my neighbor, with a mid 90's ford V-8 4x4 said that he had tried castrol high mileage, and that it was a synthetic blend, and his truck developed major oil leaks. his mechanic stated that the synthetic blend had weakend the seals, and told him to run a straight 15(i think) weight oil for a short time, drain it and go back to a convential 10w40 oil. Is any of this story true, and is the high mileage oils offered 2-day
synthetic blends, will they hurt my truck if i swithch, or help? and is it even a good idea to switch from what i am running now? I know a lot of questions, but i am so confused with all the oils available 2-day. want the best for my truck. any answers would be appriciated. Thanks, and god bless.
Oct 10, 2010 at 1:50 PM
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JACOBANDNICKOLAS
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Synthetic oil is is better for a few reasons. First, unlike conventional oil, synthetic oil isn't affected by temp. If you use 5W30, that is what you have all the time. Conventional oils get heavy under cold temps and tend to thin in extreme heat. Also, the molecular structur of synthetic is that is tends to stay where it belongs providing immediate liberication.

As far as the high mileage oils, most are not synthetic blend. They have additives to help seals and gaskets from leaking. If you want a blend, you need to get one.

We use Valvoline at out shop. Never have I had a problem with the Dura Blend or the Max Life. Also, it doesn't hurt to switch from conventional to synthetic.

I will leave you with one final thought. Your truck requires 5W30 oil. In the newer engines, the tolerances are so tight, the thinner oil can get to where it needs to be quicker. That is wy GM (amoung the others) have switched. There are even some VW that take 0W20. Talk about water. (LOL)

If you have other questions, feel free to ask.

Joe
Oct 10, 2010 at 10:38 PM
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SUZIEMAC43
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I want to find out due to high mileage, what grade/type oil should we be using for the engine. I believe it is a 5.3L Vortec 4800 V 8 engine.

Thank you,
Sep 3, 2020 at 11:31 AM (Merged)
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TOOOMANYTOYS
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What type of oil are you putting in? Also what is your oil pressure reading once vehicle is hot. If you oil pressure is normal i would sugguest 10w40 high mileage oil. If its lower than normal you may want to switch to a 20w50.
Sep 3, 2020 at 11:31 AM (Merged)
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PAULF327
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I use 100% synthic oil and have been told that you can go 7,000 miles between changes. 95% of my driving is highway miles. So I was wandering if this is true or not?

Thanks

Paul
Sep 3, 2020 at 11:31 AM (Merged)
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TXHOTROD
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Yes that is true. You can even go longer if you change your oil filter every 5000 and change your oil every 10,000
Sep 3, 2020 at 11:31 AM (Merged)