• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

Occasional Oil Burn?

Share this page

Webb Sledge

Webb Sledge

Jedi Warrior
Offline
Is it uncommon for a TR6 to burn small amounts of oil under hard acceleration? This engine only has 4000 miles on it, and the rings and valve guides were replaced with new parts when it was rebuilt, so it's not that the engine is worn. Since switching from 20W-50 Castrol to 10W-30 Synthetic, I have noticed some occasional blue smoke under hard acceleration.
 
Is 10w30 oil specified for a TR6 at what ever ambient temperature you are operating the car in? I would think a 15w50 synthetic would be more appropriate. Remember, the specified clearances inside the motor were arrived at with oil closer to the 20w50.
 
/ubbthreads/images/graemlins/iagree.gif jessebogan's correct.
These engines were designed (ie manufacturing clearances) with much heavier oil in mind and certainly not synthetic.
The "runnier" oil is certain to get past the rings and valve guides a lot easier than a heavier weight oil.
Won't do any damage but it is expensive oil to go burning in copious quantities
 
Hi,

I agree that 10w30 seems pretty light. According to a 1975 TR6 owner's manual, 20w50 is good for temps from 14F on up, 10w40 for temps consistently below 50F.

Plus, synthetic oil tends to get past seals, rings and guides more easily than non-synthetic. That's one reason I won't use pure synthetic in older design engines, which tend to have greater tolerances than modern ones. (Note: I *do* use partially synthetic, blended oils.)

Most synthetic oil also has too much detergent for old-design engines, which need a bit of coking on surfaces for optimal cylinder sealing and best compression. Any oil that's listed as "extended mileage" has a lot of detergents. You can find some non-synthetic oils that are heavy in detergents, too. To be fair, de-coking - by switching to a high detergent motor oil - is probably more of a concern with an older engine that has some wear than it is with a fresh rebuild.

Finally, swtiching to sythetic oil at 4000 mi. might be a little early. Most references I've seen say to stick with non-synthetic during at least the first 6000 to 9000 miles after an engine rebuild. Synthetic oil is actually too slippery and can cause the cylinder walls to glaze, after which the piston rings may never fully seal.

The above mileages are based upon a first oil/filter change at about 500 miles, after the heaviest part of the break-in process. Then a change at 2500 mi. when most break-in is completed. After that, regular changes at 3000 mi. intervals. So, the 4th or 5th oil change would be the first to use any sort of synthetic oil.
 
Ok, that makes sense. And if that's the case, is it safe to mix synthetic/non-synth oils? Is it safe to mix different weights? I pretty much stick with Castrol, but out of curiousity, is it safe to mix brands?

thanks
 
[ QUOTE ]
is it safe to mix synthetic/non-synth oils? Is it safe to mix different weights? I pretty much stick with Castrol, but out of curiousity, is it safe to mix brands?


[/ QUOTE ]Absolutely. My custom blend is 50:50 Castrol GTX 20W-50 dino and Rotella T 10W-40 synthetic. The Rotella is an excellent oil designed for extended drains on diesels. I have over 15K miles on this blend with no oil burning (oil dripping is another matter though).
 
Back
Top