Engine Oil Weight vs Temperature


9 replies to this topic
  • wweagleflyer

Posted June 14, 2013 - 04:36 PM

#1

I am getting conflicting information about what oil weight to use in the summer. My bike is a 2006 YZ450F and the manual says to use 20W-40 for temperatures over 40 F, and 10W-30 for temperatures less than that. However, I can't even find 20W-40, and 20W-50 is hard to find, and my local shop does not carry it as a synthetic oil (only have mineral 20W-50). Two different shops in town say to only use 10W-40 all year around, but I have had guys at shops say things that are totally wrong before, so I tend to follow the manual.

I have read this thread:

http://www.thumperta...t#entry10504900

where Gray says that he uses 20W-50 during the hottest months, but I am looking for a temperature at which I should switch. My hottest riding days will be in the mid 90's F. Should I just stick with 10W-40 like the local shops say?

Thanks

  • wweagleflyer

Posted June 16, 2013 - 07:02 PM

#2

Anyone?

  • grayracer513

Posted June 16, 2013 - 10:14 PM

#3

Look in your manual. There's a chart in the spec section that shows the whole range of temperature an oil will cover.

You seem to be confused by the two different numbers on the oil grade label. The number with the "W" is the "winter" viscosity, and usually the weight of the base oil it was made from. A 10W-40 oil will pour and flow like an ordinary 10 weight at 70 ℉. Additives are blended in that prevent the oil from thinning out as much as it normally would when it gets heated, so when you see 10W-40, you're looking at an oil that will test as a 10 weight at 70 degrees, and a 40 weight at 200 ℉.

A 40 weight will, according to the chart in your manual, be adequate up to ambient temps of 114 ℉. I use a 20W-50 when I expect the temperature to be at or over ninety if I'm riding desert or trails because the "nano-climate" immediately around my engine at the bottom of a rocky canyon in the badlands can be surprisingly hotter than anywhere out in the open, and I just like the extra thermal tolerance. For MX, I'd probably run my normal 10W-40 until it was closer to 100.

  • wweagleflyer

Posted June 17, 2013 - 01:49 PM

#4

Additives are blended in that prevent the oil from thinning out as much as it normally would when it gets heated, so when you see 10W-40, you're looking at an oil that will test as a 10 weight at 70 degrees, and a 40 weight at 200 ℉.


Thanks for the explanation. So if I understand what you are saying, at normal engine operating temperatures, there is little difference between 10W-40 and the 20W-40 refrenced in the manual. The main difference between the two would be the 20W would be more viscous when starting a cold engine, but at 200F they should be about the smae viscosity?

  • grayracer513

Posted June 17, 2013 - 01:51 PM

#5

That's right.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Lighterknot

Posted June 19, 2013 - 04:43 PM

#6

I just picked up an 07 450 and haven't had a dirtbike in about 15 years so I def appreciate all the info. One question though. I keep hearing info about once you go synthetic you have to always run synthetic but then I hear other people say that's just a myth or marketing thing. Thoughts?

  • grayracer513

Posted June 20, 2013 - 06:36 AM

#7

It's a myth. Synthetic oils are entirely miscible and interchangeable with natural petroleum base stocks. You can switch them back and forth or even mix them if you have to unless the product label specifies otherwise, as it might on castor oil products.

In fact, at least 50% of what most people "know" about synthetics is BS.

  • Gunner354

Posted June 20, 2013 - 12:46 PM

#8

It's a myth. Synthetic oils are entirely miscible and interchangeable with natural petroleum base stocks. You can switch them back and forth or even mix them if you have to unless the product label specifies otherwise, as it might on castor oil products.

In fact, at least 50% of what most people "know" about synthetics is BS.

Have to agree with you on this one. The saddest thing about people talking about synthetics is that many labeled synthetics aren't really a true synthetic but a highly refined petroleum oil. A huge scam!

  • grayracer513

Posted June 20, 2013 - 01:14 PM

#9

That would be the Group III oils, and the blame for this rests with Castrol and the US tort courts.

Group III oils are highly refined natural petroleum base stocks. They are so highly refined that their performance actually approaches that of true synthetics so long as things don't get too hot, too cold, or an excess of point pressure isn't applied. Most contemporary water-cooled lower RPM plain bearing engines (essentially meaning larger automotive engines) can use them without ever noticing a practical difference. The process keeps improving, too. But so does the process for making true synthetics.

The history here is that in the late 1990s, Castrol created an oil made from Group III base stocks and labeled it "SynTec Full Synthetic", on the grounds that it was so highly refined as to be a man-made product. Mobil sued Castrol, asserting that this oil was not synthetic, but simply a highly refined petroleum oil, and therefore it was false advertising to call it synthetic. In 1999, Mobil lost their lawsuit. The courts (people who know nothing about oil, tribology, or manufacturing) decided that the word "synthetic" was a marketing term and referred to properties, not to production methods or ingredients. :banghead:

But Group III oils collapse a bit quickly under the stresses placed on them by cranks with rolling element bearings, engines that run at stratospheric speeds, and extremes of heat and pressure. Even a high quality Syn/Petro blend is better than most GIII stuff.

  • Lighterknot

Posted June 20, 2013 - 02:03 PM

#10

Thanks for clearing that up. Managed to get the oil changed last night and got everything back together. I changed the filter so I added in the full liter, but the oil was just a smidge above the top line on the dip stick(I didn't screw in the dip stick, just seated it fully without turning). I didn't try to drain any out and hope that will be ok. Looking forward to hitting an SVRA this weekend and seeing if I remember how to ride a dirtbike.





Related Content

Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Reviews

Yamaha YZ450F 2017 by Chris.GVS


Yamaha YZ450F 2017
  • - - - - -
  • 0 reviews
Forums
Photo
Motocross

Thinking about Yamaha 250... by Arctic Pride


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies
Wiki
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info


Articles
  • 0 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.