OldT

I purchased a 2006 Xb in April and one of the booklets is called "Scheduled Maintenance Guide". There are several threads on valve adjusting with all kinds of differing advice from adjustments at 15K to not at all.

The booklet I received has the following:

60,000 miles or 72 months, Inspect the following, Engine Valve clearance, pg 11.

120,000 miles or 144 months, inspect the following, Engine Valve clearance, pg 19.

Depending on the year of your car this may very. In the inside cover my booklet says this is for the 2006 xA, xB, tC.

This may clear up a lot of the discussion. Please check your manual for your model and year.

bB2NER

I think I'll check my clearances at 60K. I'm using Mobil 1 so they should still be in spec when the time comes.

SodaGuy

Provided that the oil/filter were changed at appropriate intervals, the usage of Mobil 1 should have no effect on the valve clearance.

bB2NER

And you know this how? So the lack of wear on the valvetrain has no effect on valve clearance. Just when you think you've heard it all.

vintage42

Wear on the valve train (cam lobes, followers and valve stem tips) is negligible with normal lubrication. Valve clearance is much more affected by seat recession.

The valve seats are continually impacted by lips of the closing valves. Microscopic amounts of metal are both rubbed and pulled off the seats by the impact, allowing the valves to go further up into the head before they close against the seats. This reduces the clearance between the valve stem and the cam, and eventually the clearance is gone. The valve then begins not to close all the way - first it does not seal, and later it hangs open. This reduces compression. So comes the need to restore the clearance long before this happens, by adjusting the valves.

When unleaded gas was introduced, seat recession was quite a serious problem on engines that had un-hardened valve seats that relied on lead to cushion them. They had rapid seat recession and the only cure was unleaded valve kits.

Old overhead valve engines with solid lifters used to need valve clearance checking every 4,000 miles. Metallurgy is so good now that it's 60,000 miles.

Valve adjusting used to ony require a feeler guage and a couple of wrenches, but modern engines usually require shim buckets that are selected from a working stock that can only be held by dealers.

bB2NER

Yep ours has the ol shim bucket type like motorcycles.

ghostrider25

I usually check valve clearance at 15k after engine break in period and from there on every 30k it doesn't take long to do I am just conservative and careful. I also noticed the manual says nothing about changing the timing chain and gears and waterpump. I talked to a few echo owners and they have been getting it all changed at 120k and the chain tensioner will need adjustment or will need to be changed prior to that no matter what oil your running, but definently a bump for mobil hope your staying with factory filters though. I just change the filter at 3k and add a bit more oil and do my oil changes at 5k

vintage42

Are you able to check and adjust the valves on the xB yourself? Or are you saying you can check the clearance, and if adjusting is needed with the bucket shims, you take the car to the dealer who has the shim assortment?

I've been doing the opposite. My Mazda truck has been 150K with oil changes every 2500 miles and the filter changed every 5000 miles. Am doing the same with the xB. In a car where the factory interval is 5K miles for oil and filter changes, I find it easiest to increase the frequency of the oil change rather than the filter. The oil does become dark by 2500 miles and is easy the change. The filter does not have anything perceivable in it by even 6500 miles, and is a mess to change. Read Scott17's post at:
https://www.scionlife.com/forums/vie...=59333&start=0

ghostrider25

I just check the clearances and take it to the dealer if needed.

bB2NER

I'm starting to notice xB owners that are getting up there in miles. Has any of them had their valves adjusted?

vintage42

The clearance changes mostly due to erosion of metal from the valve seat and pitting of the valve lip. The contact area of the lip and seat is essentially in the combustion chamber and is not lubricated by oil.
The other thing that can affect clearance is wear of the cam lobes and the cam followers. This area is lubricated, but valve train wear causes much less change in clearance than valve seat recession.
So the type of oil used has little effect on valve clearance.

bB2NER

I'm fully aware of that vintage42.
I'm wondering mostly from the owners that have high miles (60k or more), who has actually had their valve clearances checked. If so, were any out of spec?
No one has really addressed this subject so far and the high milers I've seen never mentioned if they had this checked out per the service schedule.