syntec 5w40 or 10w40

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Jun 17, 2004
Ive been running the syntec blend 10w30 lately in my 98 xj 4.0 motor and its been pretty happy (got it for almost free from a friend that works at autozone). Ive been thinking about switching to the syntec 5w40 or 10w40 based on how well it looks and how good the VOA looks. I know the 4.0s like 40w oils and have been wanting to go to a full synthetic for a while. opinions would be great.
Either would be just fine. 5W40 Rotella T or Mobil 1 should do the trick. Oops, I just re-read your post. I guess the Syntec would be ok to. I have never used any of it but I would imagine that it is good stuff to. [ July 01, 2004, 08:46 PM: Message edited by: KW ]
well I have thought about the M1 also Im just bouncing ideas off trying to get some other feedback. I had just seen some really good support for the new syntec xw40 oils and was considering that. *btw Im looking at this as a year round oil, MD and VA so thats something else i want an opinion on is if it would be too thick for winters in these areas as ive always just used 10w30 all year. [ July 01, 2004, 09:29 PM: Message edited by: MariusVT ]
You'd probably be fine with the 10w40 since you are using 10w30 now and a synthetic will flow better in the cold. What is the coldest it normally gets in your area? If you say 10 F then I would go with the 10w40. If you say 0 F the 10w40 is probably still fine, but you may prefer the 5w40. But I am wondering if the Syntec is a Group III "synthetic" oil and, if so, you would get a better oil for not much more money with Mobil 1 which I understand to be a Group IV synthetic.
Originally posted by TallPaul: But I am wondering if the Syntec is a Group III "synthetic" oil and, if so, you would get a better oil for not much more money with Mobil 1 which I understand to be a Group IV synthetic.
TallPaul, I just put the Syntec 10W-40 in my car this morning. Actually, I can get Mobil 1 a tad cheaper. Mobil 1 is all PAO, but I don't consider it the superior product. Syntec has some PAO, Slack Wax, and is GpIII. The specs. look excellent. It's a very light 40wt. It's not your run of the mill GPIII. [ July 02, 2004, 10:23 AM: Message edited by: haley10 ]
Originally posted by 02supercrew: If the 10w30 has been working for you, why change at all?
The 10W-40 Syntec is a very light 40wt. 13.1 @ 100C and has a much more robust additive package than does the 10-30 blend. It's also A3,B3 rated. It might be an improvement for this particular engine.
Im looking at the additive package, and the 4.0 is getting broken in at 102k. the 40wt is a thin 40 so i was thinking it wouldnt be too much thicker than the dino that was doing 3k OCI, Im just looking to go to a 6 month or 5-6k OCI. And there is the whole point that the 4.0 seems to really like 40wt oils.
Originally posted by pbm: Haley 10 : What is "slack wax".
I am not a chemist, so you have to do some searches. I was speaking of Shell XHVI 5.2 Slack Wax can be hydrocracked into making a very high viscosity index/ stable blend stock or Group III base stock, better than starting with a Group I. People think of VI improver as being a bad thing and breaking down, but not necessarily so with some of the newer technology. Of course Exxon/Mobil and Chevron/Texaco have similar processes. The board may crucify me, but Petro Canada may also have some Group III technology that will rival true synthetics. Sorry i couldn't answer the real question.
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