Do you use synthetic oil?

[SomeOldBlindMan]

Taco still has original oil, as it is still under 2k miles...

[Johnny Mullet]

I use Synthetic Mobil1 in my engine and change the oil now at 7500 miles. I used to go 5000 miles on conventional oil, but the synthetic stays cleaner much longer. I also use Syncromesh in my trans which is also synthetic.

[whitevette]

Originally Posted by johnmyster

I'm of the opposite school of thought.

And I'm not convinced a thin oil will pump up measureably faster than a thick one. My oil pump is a positive displacement pump. It's spun by the engine. It's going to move the oil. Non-negotiable.

The engine-driven oil pump IS a positive displacement pump. But let us look at the intake side of this positive displacement pump. Immerse this pump into a thick liquid, and things begin to appear differently...the thick stuff is not pulled as readily into the pump suction...it tends to "cavitate". This negative pressure oil is not being delivered to the mains...flow has been slowed; flow is what lubricates, not pressure. Less flow is less lubrication.And less cooling. Film strength is not pressure-related.

[johnmyster]

Cavitation will happen at -15 psia. Given that my oil pickup is an 8 inch tube and that my coldest starts are roughly freezing, I don't think I'm in any real danger of pickup issues.

No, but flow is pressure dependant.

If my mains flow enough that pressure drops, then my cam will starve. Or vice versa. You have to have sufficient pressure to lubricate all parts. I have to have sufficient pressure to keep my lifters pumped up. If my thin oil flows too much to some passages, pressure, and thus flow will drop to others.

This is why blanket advertising statements don't work. Be familiar with your equipment. Have a handle on your needs.

And while your owner's manual may tell you what weight of oil to use, the engineers didn't really care about bearing clearances at 150k miles. There are a few valid reasons to change based on use, climate, and mileage.

[whitevette]

Originally Posted by johnmyster

Cavitation will happen at -15 psia.

No, but flow is pressure dependant.

You have to have sufficient pressure to lubricate all parts. I have to have sufficient pressure to keep my lifters pumped up.


And while your owner's manual may tell you what weight of oil to use, the engineers didn't really care about bearing clearances at 150k miles. There are a few valid reasons to change based on use, climate, and mileage.

You are correct. High mileage, high load engines live in a different environment than econoboxes. There is an argument for all opinions. One thing we tend to lose sight of is...folks who neglect their oil level, change life, oil source tend to go just as far...or for just as long as the more fastidious of us. Which says what about the dino vs. synthetic argument? Or the 3K vs. 30K change? I STILL maintain "oil is oil". Clean may be a personal choice...but I feel better about "clean & cheap"!
This tread is long enough, yes?

[bikin' Ed]

Originally Posted by Frank Lee

That changing the oil filter twice as often as the oil seems bass-ackwards to me. For one thing, I even have an owner's manual that specifies changing the filter every other oil change! For another, really, what do you think you're draining out? Is there so much gook in there that the filter media is at capacity??? I doubt it! What is the nature and source of all this gook? Hell, my old V-dubs didn't even have filters!

All oil filters have a bypass valve. This valve allows unfiltered oil to be recirculated thru the engine. The valve opens on an as needed basis. If your oil filter is dirty, it is needed more often. Your old V-dub, being air cooled didn't have the tight tolerances of today's water cooled engines. Therefore the larger particles of crud just flowed right thru. I love the old bugs, but if they had really been that good, they could have been cleaned up to pass US emissions standards.

[Brian03cav]

i use to put full syn in my focus (mobil 1). but i had that since it was new, and i drove it pretty hard. the full syn did have a good feel to it, and i noticed a difference as soon as i switched from the early miles on the car.

with my new car (in sig) i have almost 97,000 miles on it, so i've been putting high mileage in it since 89,000 (when i got it). i always heard that putting full syn in a car that never had it into high miles that it might leak. or maybe next time i will switch to full syn?

[Will]

I, of course, started out with conventional oil after the rebuild to let the engine "break in" better. I changed that oil at 500 mi, 1,000 mi, 2,500 mi. I switched to Royal Purple after about 5,000 miles. Yes, I noticed a difference with Royal Purple vs. conventional. Now I do about ever 7-8,000 miles. I cannot get Royal Purple by the quart around here anymore, only by the jug. I am switching to Quaker full synth. now.

[Lazarus]

I use synthetic(amsoil) in auto transmission and just run Rotella T 15w-40 with 10k intervals.

[whitevette]

Originally Posted by IndyIan

I think the bad reputation comes from the F150 owners who have 0W20 recommended by Ford. 20 weight oil starts to sound like a bad idea when your engine has been outputting 150hp for the last 10 minutes pulling 12,000lbs up a 8% grade... Worst case scenario for sure but its hard to change your oil when you're half way up...
Most of the time engineers get trumped by the bean counters so I don't always think what is recommended is always best.

Bean counters are money-oriented ! Every thing they think or do is money (profit). The bean counters are running this society right into the ground.... As a R&D engineer, I had to subject my proposals to the bean-counting management...so "they" could shoot all kind$ of hole$ in my designs. I'm so glad to be free of this madness....

There is a fact I learned years ago...about oil viscosity: The greater the "spread" on the viscosity numbers ( ie, 10W40 is "wider" than 10W30), the longer the polymer linking to make it behave in a broader fashion ... at the cost of lubricity at these ranges. In other words, 30 weight is the best oil (generally) on the planet ...disregarding cold start ... everything else- for street use- is a variation on this weight. 10W40 is more compromised than 20W40 (Pennzoil used to make a 20W40 oil ... I was a religious user of this). 20W50 is a pretty wide string. Lower lubricity? I don't go there, anymore.