Synthetic Engine Oils, whats the skinny?

[custom442]

Hello guys, I use Royal Purple 5W30 on my truck engine. It feels a lot of vibration for just being a truck, and also for being a manual. It might be a placebo effect but I feel less vibration after changing the oil in this thing. Why does synthetic oil thin out so much when it gets old compared to other oils?

What's really the best synthetic oil and why? Also is this stuff going to make my engine run longer or am I wasting my money? (oil change every 3,000-3500 miles) Should the viscosity of the oil be changed from manufacturer spec after the engine gets older?

 

[billyjack]

I use Mobil 1 10W-30 religiously in my wife's DD. It's a Buick Rendezvous with the 3400V6. They were notorious for valvetrain noise, especially upon initial startup. Hers has 130K on the clock and still runs and sounds fine. I change oil every 4,000 miles. I still use mineral oil in my older cars with 3,000 mile or lower change intervals. Based on my interpretation of information provided by GM over the years, synthetics definitely have superior lubricating qualities, but don't necessarily extend the change intervals by a significant amount.

Bill

 

[megaladon6]

Why does synthetic oil thin out so much when it gets old compared to other oils?

uh, actually it doesn't. it will actually stay thicker for the same miles as it doesn't break down as much.
hands down, no question, 100% guaranteed, MODERN synthetic is a better oil. the ONLY negatives are that if you have a flat tappet cam, no syn oil contains any/enough ZDDP additive (not that i know of at present). but they do make a zinc additive you can put in. and on some engines with loose piston ring tolerances you have slightly more oil burnt in the cylinders. this is due to the ability of syn to truly stick to and form a film on metal.
you will hear stories of how syn will kill seals and gaskets--that's from stupid people who listen to 30yr old research. yes, it was a problem then. THEN!!! not now. especially with new seal materials.
i work for an aerospace bearing manufacturer (turbine, rocket engine, satellites, mars rover, helicopter transmissions, turbo's, etc, etc) and we go through thousands of gallons of oil and grease a year. almost all of it is synthetic. i'm pretty sure that the few ones that don't ship with a synthetic lube on them are supplied with it by the customer.

What's really the best synthetic oil and why?

i asked my engineer about this awhile ago (he's a lube specialist) and he said Mobil 1 for automotive. and personally i do like it more than the others. you'll also note that nascar, GM, BMW, ME/BE, ferrari, porsche, maseratti, bugatti, toyota, and other major companies spec it on their cars. and i believe it's what's usually used in F-1 and leMans engines.
will it fix issues with the engine? not likely. it can quiet valvetrains, but it's not a miracle cure. but it has been proven to help engine last longer, even at 6000mi change intervals (which is what i do on my diesel--5w40 truck and fleet). people have tested the oil and found it's good up to 10000mi but i don't trust it that far. and if you plan for 6k and go past, you know you're still fine.
stay with the same viscosity, unless it's a diesel engine (normally 15w-40) 5w-40 is perfect, if it's a diesel rated oil, on truck motors and 0w-40 can be used on the car diesels like VW if it's a newer one. mine doesn't like 0w too much and i'm going back to 5w.

 

[shotgun]

I use Mobil 1 (0-30)in my wives SV6 minivan, newer engines are designed to handle the lack of addiatives in todays oil.Change it when the computer says to, about evrey 6k miles.

Use Brad Penn semi-syn "offroad" oil in my driver and race car.It has the best of both worlds.

 

[86Cutlass383SR]

Here's a good read I stumbled across. Not being an engineer myself, I don't know how much is fact or fiction. It is imformative.

http://www.nordicgroup.us/oil.htm#Introduction

 

[megaladon6]

good write up, but i do have to disagree with him about the 3000mi "myth". he is correct in that standard oil can last much longer. but it depends not only on outside weather conditions (dust, heat, etc) but also on HOW you drive. if you drive 5mi to work, the oil will not attain the proper temp for the additives to work and break down the carbon/other deposits. you also may not boil off the water in the oil (humidity). both of these, and other, factors lead to a much shorter life span. BTW, this all applies to syn oil too.
also, how many parts of this country have flat ground, with low dust, and a temp range of 40*-80*F? everywhere else either is "severe service" or is damn close.
when i was a mechanic, i saw a number of cars with oil change caused problems because they went by the "regular" service interval. then you have cases like VW who was recommending a 6k interval on standard oil. they replaced a loooot of engines and went to a 3k or synthetic 6k interval, with the syn being preferred.

 

[86Cutlass383SR]

Very true. Oil collects contamination and pulls it away from the wear surfaces. If the oil don't have a chance to evaporate the moisture, that would be a severe usage condition. It should be changed more frequently than if you drove 20 miles to work. Syn oil does have better lubricating abilities, but if your oil is contaminated it will still wear your engine at an elevated level, no matter which type of oil is in it. It will then need to be changed more often regardless which it is. I agree with Megladon.

Your driving conditions and environment are differant than mine. What works for you may be differant for me. I've never seen an engine eat itself with too often an oil change. Wait too long, and it may be too late. That's exactly why you change oil in a new motor after the first start up. To get rid on the contaminents. It's only got 30 minutes use, how can the oil be bad? The oil isn't bad and still lubricates good. It's just full of junk that's eating the bearings and wear surfaces. But then again, if you drive in a clean environment and your oil doesn't have a lot of junk in it, it may last 10,000 miles or more.

Automobiles use comsumables. They are replaced to make other parts last longer or run better. Spark plugs, antifreeze, tires, wiper blades, and oil.

As the old Fram commercial said, "You can pay me now, or you can pay me later." I'd rather change it too often than buy a new engine because I waited too long. Besides, it's a *man-thing*. Get your butt out there and change that oil! 😀