Hello,

I just got off of the phone with Mobil 1 tech he strenuously recommended AGAINST using synthetic oil. My 75 2.0 has either 133K or 33K on it, I suspect the engine has been rebuilt because (a) it runs very well and ( it does not leak a drop of oil.

The tech(?) stated that Mobil1 synthetic has many more detergents then a conventional oil and that it is much thinner then a similar weight conventional oil. He said that the oil would clean the engine and in the process destroy some of the seals and since it is thinner it would leak.

I have some understanding of the differences between the two types of oils but do not have any practical experience and do not believe his point about synthetic being thinner since a 0W-30 and convential 30 should have the same viscosity at operating temp.

I know that this is a topic of heated debate but I want to use synthetic since I believe it will be better protection for my engine. I would like your experience as a group re: switching from conventional to synthetic in a higher mileage engine.

Thank you,
Dan

And I have heard that though leaks MAY have been an issue in the early years of synthetic oils, that the problem was solved years ago (due to seal expanding additives being added to synthetcs just like do to Dino oil).

But the factory engineer should know best I guess......

I have used Redline or Mobil1 for years (and now Royal Purple) in my cars (240Z, Ferrari 308 and all my imports). In my '69 911 I used Kendall GT-1 30w.

I plan to use synthetic in my 914 (20k on rebuilt - but it leaks like a sieve anyway).

QUOTE (solex @ Mar 16 2005, 04:17 PM)

I would like your experience as a group re: switching from conventional to synthetic in a higher mileage engine.

i think it's probably the product liability avoidance spiel.

here's how they see it: you have an engine with 133,000 mi on it. you change to Mobil-1. a month later you drop a valve seat or break a ring or something that would have happened anyway and you're on the phone threatening lawsuits because they "RECOMMENDED it!

not gonna happen.

there's something like a billion and six undocumented miles on my 911. i changed to Mobil-1 15W50 2 years ago when i got it running. it has run flawlessly in conditions ranging from 5F startup to half a mile on an August afternoon with a busted fan belt.

it leaks no more now than it did 2 years ago. maybe less.

so - i know better than to RECOMMEND you change - but you asked for my experience, and that's it...

just use regular stuff. if your cars burns alot of the synthetic oil, it will leave crappy deposits that wont come off of your spark plugs.

EDIT:if your car burns alot of oil

Im a firm believer in synthetics. If your car has 133K on it, stick with regular oil. Synthetic wont destroy seals, it just cleans all the sludge off of them, thus allowing for more leaks. I use synthetic, my car leaks, but I just deal with it. The added protection is worth it in my opinion.

I hope Sammy Gore will chime in on this. He works at a refinery if I recall, and knows his oil. He'll correct me if I'm wrong here, but this is how I understand it.

The comment that synthetic oil is thinner than mineral oil of the same weight is bogus. That's like saying that wooden yard-sticks are longer than metal yard-sticks. An oil's weight is a measure of how long it takes to drain through a specific sized orofice at a specific temperature. If two fluids have the same Centistroke rating then they are by very definition the same "thickness" (at that temp) regardless or whether they are mineral oil, synthetic oil, or maple syrup. I think the the Mobil guy was full of crap and 'avoiding liability' like Rich said.

-Ben M.

My 951 would leak slightly with the same weight Mobil 1 as the conventional oil I was using. No problems on the Range Rover, though. It's gonna go in the Durango as soon as the dealer stops giving me free oil changes

QUOTE

I use synthetic, my car leaks, but I just deal with it. The added protection is worth it in my opinion.

And - synthetics are not as succeptible to breakdown at higher temps.

I use Amsoil Series 2000 Synthetic 20W-50 Racing Oil in mine. The highest temp I have seen using this oil is 130 in stop and go traffic for 2hrs. Highway temp for doesn't even move the needle! I have no leaks. Check the web site at amsoil.com

QUOTE

The highest temp I have seen using this oil is 130 in stop and go traffic for 2hrs.

Do you have an oil cooler? 4 or 6 cylinder? Isn't 130 incredibly low? Operating temp should be at least 180 IMHO. I wouldn't think any oil *ALONE* could hold teps down like that.

Only cooler is factory. I do have the deep sump. It's a 73 1.7 with the the "BIG Bore" kit and few other performance items.

QUOTE (BMartin914 @ Mar 16 2005, 08:49 PM)

Isn't 130 incredibly low?

depends.

izzat F or C ?

i hit 130C in my GTI a few times before i removed the plugged-solid AC condensor in front of the plugged-solid radiator ...

130C is pretty darned hot - 135C was my "shut down" limit ...

the temp reads in F.

QUOTE (akellym @ Mar 16 2005, 05:55 PM)

the temp reads in F.

I would calibrate my gauge.
Anyway I run dino oil in my motor right now. It leaked a little. Now I THINK I got the leaks fixed and will run synthetic. I have new front and rear crank seals push rod seals and oil cooler seals. etc.
No idea of how many miles are on the engine but all the miles I put on are HARD. including 2 driver Autocross duty through the summer.

QUOTE (solex @ Mar 16 2005, 01:17 PM)

The tech(?) stated that Mobil1 synthetic has many more detergents then a conventional oil and that it is much thinner then a similar weight conventional oil.   He said that the oil would clean the engine and in the process destroy some of the seals and since it is thinner it would leak.

Dan,
This is from the Mobil 1 web site:

Mobil 1 does not cause leaks. In fact, new Mobil 1 was tested in dozens of industry standard and OEM tests to prove its seal performance. It is fully compatible with the elastomeric materials from which all automotive seals and gaskets are made. If an older engine is in good condition and does not have oil leaks, Mobil 1 provides the same advantages as when used in a new engine. ExxonMobil recommends taking measures to repair the leaks, then using Mobil 1. ExxonMobil also recommends following the automobile manufacturer's manual for the proper oil to use.

Sounds as if they are trying to say that if an engine does not leak then it won't leak with Mobil 1; but if it is already leaking then it will leak with Mobil 1 unless you repair the leaks

Thank you everyone!

I think I will give synthetic (0W-30)

I used to run shel rotella dino oli 15w40. I switched to the synthetic shell rotella 5w40. It runs great. Better that the dino. And since it is diesel oil it cleanes the inside like ive never seen. I could eat off my rockers. It also got a little smother with the synthetic. Your call.....
PS the shell rotella synthetic it like $16 bucks at Wally Martin for a gallon. The dino is like $8.....

whats the benefit of a diesel oil? (rotella D... etc?)

QUOTE (solex @ Mar 16 2005, 11:14 PM)

I think I will give synthetic (0W-30)

waittaminute...

you asked about synthetic oil. that is not a free pass on ultrathin synthetic oil -- that stuff works great in NEW, water-cooled, hydraulic-lifter engines.

don't use oil of a (significantly) different grade than specified. 15W50 is very popular with the aircooled crowd. maybe even 10W40 especially if you live in a cold climate.

Porsche recommends 0W40 for their new engines -- which are water-cooled, hydraulic-lifter engines.

My question is what smells better when it leaks onto the heat exchanges? Synthetic or traditional? Maybe they could come out with scented oil for 914's!

I switched to mobile one and my 3.2 started leaking really bad from the oil return tubes.
My plan is to swap out the oil return tubes and continue to use mobile one, since that's the only place its leaking from.
It definetly runs better on Mobile one.

Yea definately DO NOT use that thin 0w-30 stuff. go withthe thicker 15W-50 it is closer to the viscosity of what the engine was designed and built for.

Royal Purple is what I here is the good stuff nowadays.

http://www.royalpurple.com/homer/homer.html

Royal Purple passed my testing... Its the Best Synthetic for an aircooled engine by far.. In Second place is Valvoline.

Redline did eequal to Royal Purple but its more expensive.

ALL I run in my engines is synthetic oils..

The oil in the 912E has 10K on it now and has went 17K between changes! I only change the oil when I see a puff of smoke between gearshifts!

The oil in my Bus engine hasn't been changed in over 2 years- Its valvoline.

QUOTE (Jake Raby @ Mar 17 2005, 11:54 AM)

ALL I run in my engines is synthetic oils..

cool, me too -- but this thread is about a different question...

would you suggest that a person change to a synthetic in a high-mileage engine with unknown history, or not?

i've done it without incident in my last 3 cars -- an ur-GTI, a Subaru, and the 911.
with each changeover, i've replaced the oil and filter a little sooner than i would if i knew the history, figuring the new and different detergent package could stir up and dislodge some gunk. and then i changed the filter but not the oil halfway to the next scheduled oil change.

not until recently did i get a proper filter-opening tool so i wasn't able to check for unusual quantities of unusual gunk following those changeovers, but the filters i have cut open, and the oil screen in the 911, have all appeared fine. i'm not saying it's impossible for a new high-detergent synthetic to dislodge big quantities of crap, especially if maybe the prior owner used non-detergent oil (which you have to look hard to find, these days...) or PennzOil or something. but i haven't experienced ot personally...

Would synthetic work during break-in for a new never before run engine?

You will probably have some trouble getting the rings to seat, at least that is what I have heard in the past.

I am told to never use synthetic on a new or never-run-before rebuilt engine.

NEVER break in an engine on synthetic. Rings won't seat and bearings won't run in very well. I switch at around 2K miles....

I would switch an older engine to synthetic only if the oil pressure was monitored with conventional oil and then compared to the pressures achieved by synthetic... A worn engine can be damaged from the lack of viscosity from synthetic if you don't have enough pressure due to worn bearings and open clearances.
Other than that it should be fine.

QUOTE (Headrage @ Mar 17 2005, 12:56 PM)

Would synthetic work during break-in for a new never before run engine?

conventional wisdom is that synthetics "work too well" for break-in. the purpose of break-in is to wear down the high spots and discontinuities on the high-pressure areas like the cam lobe/lifter interface, and seat the rings - by which is meant the rings and cylinder walls burnish each other to a perfect fit.

you need some friction for this initial high-rate 'wear' to occur.

i've always broken in engines using a good conventional oil - like Valvoline Racing oil and never had a problem with ring seat or cam wear.

but i don't build nearly as many engines as Jake and some of the others guys, so i'll be very interested in their opinions on this subject too.

What is the recommended oil pressure/engine RPM in a warm engine?

With the oil at the max temp it normally runs....

A BARE minimum of 40PSI at 3,000 RPM....

And a minimum of 14PSI at the same temp at idle..

Note: These are my specs and everyone has their own..

0-30 is too thin in my opinion. 15-50 or 20-50 is the ticket

QUOTE (Jake Raby @ Mar 17 2005, 10:00 AM)

NEVER break in an engine on synthetic. Rings won't seat and bearings won't run in very well. I switch at around 2K miles....

From the Mobil 1 web site:

You can start using Mobil 1 with SuperSyn Technology in new vehicles at any time, even in brand new vehicles. In fact, Mobil 1 with SuperSyn Technology is original equipment (it is installed at the factory) in:
Aston Martin
Bentley Amage and Bentley GT
Cadillac CTS, XLR, SRX and STS
Chevrolet Corvette
Dodge Viper
Mercedes-Benz AMG vehicles
Mercedes SLR
Mitsubishi EVO
Pontiac GTO
All Porsche vehicles
One of the myths that surrounds synthetic oils is that new engines require a break-in period with conventional oil. The fact is, current engine manufacturing technology does not require this break-in period. As indicated by the decisions of the engineers who design the high-performance cars listed above, Mobil 1 can be used starting the day you drive the car off the showroom floor.


So if the engine was rebuilt right, to new specs then.....

QUOTE (ChrisReale @ Mar 17 2005, 10:16 AM)

0-30 is too thin in my opinion. 15-50 or 20-50 is the ticket

From my understanding the weight of the oil at operating temperature is mostly determined by the recommended oil pressure over an RPM range which is base on the required tolerences of the bearing surfaces.

For instance, if the recommended pressure of 40 psi at 3000 RPM is achieved with 30 weight oil then using 50 weight oil at the same temp and RPM will give me more pressure but will not necessarily increase the flow of oil.

Pressure does help keep the bearing surfaces apart but more flow helps with heat dissapation (from my beetle days I remember Gene Berg stating that air-cooled engines are also oil-cooled). So a balance must be struck between pressure and flow.

Based on what I have read and what you are all saying; I really need to monitor the pressure inorder to select the appropriate oil weight.

Thank you again!

You can do all that, or just go with the recommendations you get here, which were accumulated over years of trial and error by garage mechanics like myself, and pro engine rebuilders like Jake. 15w-50, or 20w-50 synthetic oil is what you should use.

QUOTE (Tom73 @ Mar 17 2005, 01:22 PM)

From the Mobil 1 web site: You can start using Mobil 1 with SuperSyn Technology in new vehicles at any time, even in brand new vehicles.... So if the engine was rebuilt right, to new specs then.....

what they *don't* say is that they are talking about vehicles, and we are talking about engines. what they conveniently leave out is that all the manufacturers of high-performance engines run in their engines on a dyno before they go into those vehicles. IOW - the break-in is done and the rings seated when you get the vehicle.

i don't think this changes anything.

don't try to break in an engine using eynthetic oil. once it's run in, change to your heart's content.

20/50 summer, 10/40 if you have a mile dinter and 10/30 if it gets cold as the North pole at your house.

The Mobil 1 ad is TRYING to sell you oil.....

Mobil 1 sucks the big one in a TIV every time I have tested it. One of my FP racers had to run it at a particular race and the engine ran oil temps 30 degrees hotter than it did the day before at the same track with Royal Purple... When he switched back to Royal purple the temps dropped again.... Just because it works and is recommended for a 911 doesn't mean squat to our engine.

FWIW in all my days of cooling system testing and R&D in general I have never seen changing weights or types of oils impact HEAD temps the way that Berg describes... All his synthetic testing was done when Amsoil was the ONLY synthetic and then it still sucked the same as it does today in our engines..... I have proven that compared to 6 other oils in the same engine in the car and on the dyno....

Jake,

What effect have you seen on head temps? I don't know what Berg said.


Andrew

Virtually nothing... As long as lubrication is delivered at the same volume the type of oil didn't impact it at all...

The springs, guides and valves are the only thing the oil cools.. While friction reduction is nice and always good the head doesn't seems to respond temp wise to the difference in oil...

Berg said 'Cooling the oil doesn't cool the heads" and thats right... BUT he doesn't say that "cooling the heads doesn't cool the oil" and thats the big issue..

To cool the heads better you have to "out think" the engine...