1. I've heard that 'heavier' grades of motor oil help carry heat away from the engine. But the oil in our 7s gets burnt, not circulated, right? Can I expect any kind of cooling benefit from a heavier oil?

2. How far into 'heavier' oils can I stray b4 I start making life harder for the engine? I'm thinking that the heavier the oil, the more carbon and goo (if there's goo) that may be left behind after a cycle. Yeah, I know, high revs and a tank of MMO will knock that crap right out, but I'd like to skip out on causing a sizable carbon/goo bi-product if I can. Make things as easy for the engine as possible.

3. I've also seen it mentioned that 10W40 should be avoided because there's some sort of undesirable additive that is used to get that kind of "split." Would someone elaborate on this? And is this also a concern with 20W50, which I've noticed a # of 7 owners in the southern states use?

And if the answer to question #1 is yes, I'm planning on switching to 20W50 this summer. My girl's running a little hotter than she used to and I'd like to do what I can to give her a break.

Thanx much in advance!

 

Only a tiny fraction of the oil is burnt. The rest is recirculated just like any other engine. I’ve never heard of heavier oils cooling better. I doubt they do. A heavier oil would circulate slower so it may actually got too hot, but that’s just a guess.

I’d just stick with the recommended 20/50.

 

Yes, a minute amount of engine motor oil gets injected into the combustion chambers, on the average of about a quart every 2,000 - 4,000 miles.&nbsp Engine motor oil's primary responsibility is lubrication first and cooling second.&nbsp I'm not too sure if there is data on the effects of thicker versus thinner in terms of cooling effects.&nbsp The heavier weight engine motor oil is surely better in terms of lubrication (across the same brand of oil).


20W50 is the typical heaviest weight you'll see commercially available.&nbsp Keep to this limit.


I've got it here...
http://fc3s-pro.com/TECH/MODS/ENGINE...randweight.htm
The link is at the bottom.


I'd recommend inspecting your cooling system.&nbsp Staring at the oil system is not a conventional means of troubleshooting cooling problems.&nbsp The cooling system is design to primarily cooling the engine down - start there first.



-Ted

 

Yes, most 10W40 and 10W50 oils have considerablly more additives than a 5W30 or 20W50. So much that many manufactures have specificly said not to use those weights in their higher rev'ing motors.

Toyota has gone so far and refused to warrenty some vehicles that 10W40 or 10W50 oils were used in, in the some parts of the country.

The additive package to get that spread also creates additional ash load, which can lead to deposits and sludge. Some new testing also suggestes that sludge can also be created by mixing different base oils, such as parafin based oils and shale based oils.

Because 20W40 and 20W50 (and 15W50 synthetics) use a higher base oil, the additive package is considerably lower and doesn't have the same concerns that 10W40 would have.

For some additional reading try these:
http://www.motor-oil-bible.com/index-test6.html
http://www.xs11.com/stories/croil96.htm (note this one suggests that Mobil 1 is waste of money and performed no better than any other oil).
http://www.ibmwr.org/otech/oilreport.html

and my favorite:
http://www.vtr.org/maintain/oil-overview.html

 

Ted you have got to be the leader in thread-ending-posts

 

My post wasn't intended to imply that I thought that an oil change would be the best way to resolve a temp issue - Christ! I'm about to throw in a Fiero fan and restore the fan shroud and the panel from beneath the engine (both were left off when they did my engine swap last summer.) Hopefully, this will end the temp issue for me.

My curiousity was mostly revolving around questions 2 and 3. Especially 2. Knowing now that a heavier oil will provide superior lubrication is a bonus.

Thank you all for the help!

 

The panels there and in front of the rad must be on for proper cooling.

 

Picked up 5 litres of Castrol 20W50 (they didn't have Havoline in that weight.) She's getting an oil change 2 morrow morning (OEM filter.)

Thanx again!

 

I recommend Castrol 20w50. Use it all the time!
2nd gen - 195k miles w/ rebuilt engine
3rd gen - 87k miles

That reminds me... it's actually time for an oil change. Hehe