Castrol Syntec 5W30 vs Mobil 1 5W30

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Jan 18, 2003
First off, I understand Castrol Syntec is not a 'full' synthetic and Mobil 1 is; Point taken.

I also realize both are about the same price, so Castrol overcharges for their product; point taken.

Having said and understood that, I have searched the forum and I can't find any bad UOA's or any specific reasons as to why Castrol Syntec 5W30 isn't as good of an oil as Mobil 1 in daily use (for example a 5K or 7.5K mile oil change).

Can anyone provide any data or links as to Castrol not doing well in an engine in everyday use??

FYI, I am going to submit a UOA of Castrol Syntec 5W30 in our 2004 Lexus RX330 at the 5000 mile interval. It will be a few months down the road, but ..... Anyway, thanks for your help.

[ July 19, 2004, 11:31 AM: Message edited by: Curtis Newton ]
Syntec has definitely gotten a bad rap over the years, even I myself have warned people not to use it, but this was before I saw UOAs on it.

We're definitely seeing evidence that Syntec and Syntec blend work very well in the UOAs posted on here.

I don't think Syntec 5w30 would be able to last beyond 10k as easily as Mobil 1 5w30 would, however for under 10k I believe it's wear numbers would be very similar.

I often see much better sales on Syntec up here compared to Mobil 1, and the regular price per liter is almost 50 cents less, so it is in fact cheaper up here.
Thanks Patman...I am using GC 0W30 (thanks to BITOG) in my 2001 Audi A4 (2.8L V6) and just find it easier (albeit, perhaps not smarter..:) to stick with one manufacturer for my oil changes; thus, the reason why I am asking about the Syntec 5W30 product in everyday mixed highway/city use.
wow syntec and a
in one sentence, thats a first for this board!
but yeah, i think you'll be just as good with Syntec 5W-30 as you would be with M1 5W-30, if your car likes a slightly higher 30 wt oils, you may even want to try Syntec 10W-40, its only 13.1 cst@100 so its very thin for a 40 wt and a very good oil
you know, lots of people look down on the syntec line because of castrol calling grp III a synth, but who cares what they put in there as long as it works well, and to me an oil is good and is worth the money if it works well and puts out good results. If the syntec line puts out good results, but its made with group III, slack wax, and PAO, well i dont really care since the oil works well
I must say though, i'm not very fond of their 10W-30....
Some bench test comparisons of new 10W-30s:

Thin Film Oxygen Uptake ASTM D-4742
Mobil 1 397 Syntec 221 (higher better)
High Temperature/High Shear ASTM D-4683
M 3.30 S 3.13 (higher better)
NOACK Volatility ASTM D-5800
M 8.92 S 7.77 (lower better)
Pour Point ASTM D-97
M -46C S -43C (lower better)
M 8.57 S 10.39 (higher better)
Cold Crank Simulator ASTM D-5293
M 3967 S 4783 (lower better)
and one many think is not relevant
Four Ball Wear ASTM D-4172
M 0.60 S 0.45 (lower better)

All tests in early 2003
I think people didn't like Castrols attitude and advertisement. They changed from a true synthetic yet kept the synthetic name on the bottle, saved themselves alot of money and kept charging for the original formula. Misleading is what comes to mind when thinking about it. I agree they make a very good oil and there are excellent UOA's on this site to prove it. I jumped ship when I found out. I disagreed with there maketing and changed oil. I even spend more for oil now then before, just my money isn't going to Castrol, which is the only way I can tell them how I feel. Talk is cheap, action gets respect.

[ July 19, 2004, 02:58 PM: Message edited by: Steel Blue Wind Rider ]
I've done the same when i found out, and in fact I went through a series of different oils afterwards, ended up sticking with M1 and telling others not to use Castrol because of their lies, well a few years later, I've decided to give them another try. its really not a bad oil, i really wish we had more percentages of amounts of each base oil that is in this stuff, but oh well, as long as it works, use it. As for the tests comparing the M1 10W-30 and SYNTEC 10W-30, i'm not very surprised, their 10W-30 is one of their weakest oils in the Syntec line, I would like to see a comaprison of the 10W-40 against a comparable oil, too bad M1 doesnt make one in that weight....
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