Can I use 5W30 for my '93 Previa???

The reason I ask because I've learned from other groups and magazines talking about the Toyota recommends 5W30 for new cars due to the engine gelling and resulting in sludging problem. And 5w30 can easily reach anywhere in the engine faster than 10W30 & 10W40 and further reduce the possibility of engine gelling & sludging. My Previa owner's manual recommends 10W30 or 10W40. The manual also shows that temp. range is from 50 degre F. to less than 50 F with no limit. But, the '02 manual shows the temp. for 5W30 is from more than

100 degree F to less than 0 degree F. Why there is such discrepancy??? Anyway, I've always used 10W30 on my Previa and '90 Corolla. The Previa engine is pretty clean from the last time I checked when I opened the valve cover. I also use synthetic oil on all my Toyotas in early days. Now, I use synthetic oil for engine flushimg purpose. I heard that '94 and above Previa use 5W30. Is this true?? However, my '02 Highlander owner manual recommends to use 5W30. I have stocked both 5W30 & 10W30 oil. For convenient and good purpose, I'll like to use 5W30 for all my Toyotas. I figure if I can use it on Previa then I can use it on '90 Corolla. Any insights and suggestions are welcome and appreciated.

All the best, Matt

Reply to
Matt
Loading thread data ...

The oil gelling or sludging is due to either (or both) excess heat in certain parts of certain engines and/or from damage to the oil by the timing gears between camshafts. The gears mechanically shear the polymer viscosity index improvers resulting in the sheared polymers oxidizing faster than they otherwise would and thereby forming sludge. The sheared VIIs also cause the oil to become lower viscosity. The oil that tested new at a 5W-30 may now test as a 5W-20.

10W-30 oils have a lower contend of VIIs and therefore exhibit less viscosity shear. I'd recommend continuing with the 10W-30. If your Highlander owner's manual allows the use of 10W-30, that would be my preference. The story about 5W-30 circulating faster through a cold engine is only significant in very cold weather. I always use the highest viscosity oil permitted in the owner's manual. I'm now running a premium synthetic blend 15W-40 oil in my Tundra V-8, and the engine has never been quieter.

What I do is to clean the engine slowly and completely with

formatting link
Then, I use a top quality 10W-30 oil such as Chevron/Havoline, Pennzoil, or Castrol. I also clean my transmissions with
formatting link
before a complete transmission flush. I believe that it adds many miles to the life my transmissions.

Ken

Reply to
Ken Shelton

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.