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Synthetic oils

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Gary Lloyd

Jedi Knight
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I was just at the Healey forum, (to try and help them out a bit
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) and there is a discussion on synthetic oil. I found this one particularily interesting!! Any thoughts guys?? It made sense to me, and please notice that he is a Canadian!!!
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RF Thom
Senior Member
Member # 994
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posted 01-21-2003 09:55 PM
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Petrolium based engine oils break down at 280 degrees F. where as synthetis break down at 450 degrees F. Oil in the engine serves many functions one of which is a heat transfer medium, and as such can reach temperatures of 260/275 F. Petrolium based engine oils therefore do not provide a sufficient protection cushion. Remember the hotist components in an operating engine are 1st the valves then the pistons. Exhaust valve can reach 1800 degrees F. - pistons domes 450 degrees F. As the oil breaks down it turns to a black ash, [ remember 'Blacky Carbon']and is commonly found behind the piston rings eventually contaminating and stopping them from functioning. I use synthetic oil in all my vehicles. Before I retired I was a Design Liaison Engineer for GM Powertrain and had access to relative test results. I've seen data where 600 hour dyno tests [ = 100,000 miles ] without an oil change with oil sampling analysis every 25 hours showed no trace materials after the initial 10 hour breakin.
Regards, Bob


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Posts: 20 | From: St.Catharines ON Canada | Registered: Aug 2002
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Gary, I beleive synthetic Oil is a good thing for a new engine but have heard some things about excess leakage and oil burning in older engines, like mine
 
I believe Mobil 1 has a synthetic for use in older cars. I found this out using the Mobil 1 in my new Tahoe (sorry guys-my office at times) I picked the box up off the shelf and it was 5w-30 (I was almost certain that I needed 10w-30, in a different colored box. Took it home, checked the book to reassure myself and walla! the wrong stuff for newer vehiciles. I thought about keeping it for the '77 B but had heard the same thing Chuck said about burning and leaking. That stuff doesn't seem to work real well with drier if you spill it. Good luck and please post your results.
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I didn't know that there was a synthetic formulated for older vehicles!! Good to know!! You guys are a wealth of information!!
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Totally on a gut-level, no-science-involved level, I'm sticking with my Castrol dino oil.

I just don't like the idea of putting anything synthetic in or on my classic car!
 
I'm using a blend in mine right now...in the engine only...and am thinking of trying it in the transmission, but heard that I shouldn't somewhere, I think. Does anyone know anything about why it wouldn't be good in the tranny?

Bruce
 
There are engines specifically designed for use with synthetic oils and I wouldn't think about doubting the engineering reasons for this. they say use synthetic so use it.

For the rest of us the merits of synthetic oils based on thermal-breakdown may be well founded, but the too often used line that "it'll last xx,xxx miles!" bothers me because it isn't a blanket truth. The change-interval isn't automatically extended souly because of the oil you're using.

You still have to keep the oil clean and fresh. The oil will without question pick up dirt through the intake system on your car and other crud developed through the operation of the engine. Even with switching to high-quality oiled air-filters a good amount of airborne contaminants will reach the oil. Combustion blow-by and general engine-wear also are major contributors of oil contamination, both of which are lessened to a degree by using synthetics but are by no means eliminated.

In the end if you do switch to synthetics you still have to keep your oil filter changed at a good interval. Even modern engines with the best quality and maintained intake system and filters (air and oil) should have the oil filter changed on a regular basis, which is yet another debating point apparently. One of the biggest proponents of synthetic oils recommends you change your filter at your vehicle's recommended oil-change interval unless you use their special super-filter that they sell of course, then you can extend oil-filter changes to 12500-miles.

I don't know about you, but for me actually changing the oil is a simple task. Changing the filter is the chore. If I've got to change the filter, putting fresh new oil in the engine isn't a big deal, nor is it a costly one. Will synthetics show a significant improvement over dino oils changed at regular intervals? I've read conflicting reports on that one but I would suggest that if you're changing oil every 3000-or-so miles then the engine is most likely not any worse off than if you used synthetics under the same conditions (most of the beneficial claims about synthetics take the extended-oil-change approach rather than the "under the same conditions" approach).

One last note: water build-up is yet another problem to consider in the grand scheme of things (no matter what oil you're using), and can only be removed by changing the oil, and to a certain extent boiled-off with oil temps exceeding 100*C. If you're a short-hop driver, or only drive your LBC on really nice days then the water problem can be even more serious.

Want some interesting reading on the subject? Do a search on the 'net about synthetics. You'll find everything from charts and graphics explaining how it all really works to about the massive "big oil company conspiracy" to keep synthetics away from you. Yeah, it's all very entertaining.

Note: After writing all this I found at least one website that published a real-world test using various brands of dino-oil, and synthetics in 75 New York City taxicabs. After changing ALL oils at 6000-mile intervals they disassembled and examined the engines and found very little difference in any of the tested engines.

[ 01-25-2003: Message edited by: aerog ]</p>
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Bruce74B:
I'm using a blend in mine right now...in the engine only...and am thinking of trying it in the transmission, but heard that I shouldn't somewhere, I think. Does anyone know anything about why it wouldn't be good in the tranny?

Bruce<hr></blockquote>

If you have an overdrive transmission you have to consider the clutch in the gearbox. It's bathed in oil, and any PTFE or other additives can cause it to not operate properly (or so the story goes). Supposedly synthetics have been known to cause slippage and other problems also.

Regular gearboxes should work fine with any oil, but whether or not synthetics will yield any appreciable protection is yet another debate, but it certainly can't hurt.
 
Thanks for the input and thought Aerog!! I agree with Kim!! There really is no need for synthetics! I have never used synthetic in my life, and see no reason for it!! I think that the improvements in oil and the use of unleaded gas have made such an improvement over the past 20 years that is good enough!! I remember well when engines omly lasted 100,000 miles if all went well, now they last anywhere up to 300,000 miles, and I will assure you most of that goes to quality of oils now!! Thanks guys (and girl)!! 20/50 Castrol for me!!
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Gary,

I've heard horror stories about rings not seating in new LBC engines due to use of synthetic. It might be best to break in a new engine with regular oil then switch.

My 93 Mitsubishi just turned 180,000 miles all done with Syntec except the first 3,000. This is the V6 engine that's famous for burning oil at 50,000 to 75,000 miles. Didn't happen in mine. Don't know for sure if it's the Syntec, but I do know that I NEVER mix brands.

Steve
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<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Chuck Cougill:
Gary, I beleive synthetic Oil is a good thing for a new engine but have heard some things about excess leakage and oil burning in older engines, like mine<hr></blockquote>

The leakage supposedly comes from the synthetic oils being thinnner than dino oil. It doesn't create leaks, just takes better advantage of the ones you already have.

I personally use it in my 97 Escort for political and environmental reasons. I know that my 5.5 quarts don't make much diff either way, but it is something. I also run a K&N permanent air filter for the same reasons, less waste. I have been using a full synthetic and changing the oil at 7,000 miles, in between the dino 5 and the syn reccommended 10, and it all seems to be going well. I would probably hesitate to use it in a classic engine, however due to the different tolerances. Plus it is expensive stuff to let your LBC mark it's territory with.

As far as the brand new engine and the gasket thing, I understand that the oil has a lot to do with modern gaskets sealing, and that a new engine should be run with dino oil through break-in.

Just my two cents.

MattP
 
Synthetics are superior. If you have leaks, it will. If it burns it, it will. If they increase or not, I don't know. I would guess that they will, simply because a 20-50 synthetic will still pour at 20F. My quattro runs better. and shifts in the winter with synthetic in everything. I'm convinced that it kept me from blowing an engine(I was trying to) and am now glad it did. The oil gague in my tr3 loves it. My 77 ford 250 truck has had 3 motors. First, 30k, second, another 35k. With engine 3 I went synthetic, punched it out, put a honkin' cam in it, the whole deal- its a work truck, has to haul a crawler tractor, and I regularly put 2 tons in the bed. With the syn, and a twin filter kit, I change the filters once, and the other twice a year. And haven't touched the oil drain plug in 2 years.(this motor has 80k, and fantastic oil pressure) If anybody cares, I use Amsoil.

As far as a british car goes, it depends on how much, and how, you drive. I don't see any advantages unless you drive it a bunch, and it doesn't leak, or you race it. In my opinion, the old motors aren't usually sealed, efficient, or used enough to take advantage of synthetics.
 
In theory you should replace the filters at a minimum of twice a year (every six month) due to the breakdown of the filter core material itself, and that is only true using the top of the line expensive filters available from Amsoil. Although this could be partly a sales tactic by Amsoil, Amsoil recommends you change your filter at the manufacturer's specified interval no matter what oil you use (3000-7500 miles typically).

Amsoil also recommends changing oil at a bare minimum every year. Depending upon which oil and type of engine/application you're using they recommend a maximum interval of 35000 miles but sometimes as little as twice the interval recommended by the engine manufacturer (6000-15000 miles). For light passenger car use they typically recommend a maximum of 25000-miles between changes and three-times the manufacturer's recommend interval if you're using 20w50 oil.

As has been mentioned, one thing the oil cannot do is effectively discharge any moisture or combustion byproducts (acids) being carried away by the oil. Supposedly the expensive bypass-type oil filters will eliminate moisture from the oil (which is another reason they need to be changed on a regular basis). Even with bypass-filtration the oil needs to be changed regularly to elminating corrosion-causing acids that build up in the oil, and without bypass-filtration the acids AND water both need to be removed from the engine.

It would be interesting to see an oil analysis and engine tear down of your 80,000mile no-change oil and engine. Keep us up to date on the engine's condition if you have to open it up for anything.

Regards --
 
I will, its time for a tune up and the valve covers and dist. seal leak, so I'll let you know what it looks like in there. I do have a kit to sample the oil with and send for analysis, just haven't bothered yet. Now might be a good time to find out.
 
Gary,
I have used Amsoil synthetic in our 92 Isuzu work truck since it had 3000km on it. It has been drivin ridiculously hard for 347,000km more. Still hasn't been torn down but it is getting sluggish. Changed the oil filter every 8000km and oil every 24000km (didn't realize that was supposed to me "miles").
I use the synthetic in my MG race car (20/50).
I have been using synthetic in my 74 MG without any problems but have concluded, as someone else mentioned, that I just don't drive it far enough, hard enough or long enough (time) to warrant using the synthetic. I'm going to switch it back to regular oil this year and change the oil every 3000 miles or at least once a year.
Great question, enjoyed the many informative replys.
Joe
 
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