A question about engine oil changes

Why is it that my Pontiac Grand Prix GT recommended oil changes are every 3K miles or when the DIC (drivers information center) lights up and says so, while the recommended oil change interval for my Porsche 944 is every 15K miles?

I just find it strange that the Porsche would have an oil change interval that's 5 times longer than the GM engine. Any ideas, knowledge or hints?

Porsche=german
GM=american

need I say more? :p

Like he said german. but i still change mine every 3k, because i love it!

15k miles the maximum amount of miles before an oil change so long as you drive it only on clear, dust free days, on highways only, during certain times of the year, always shifting at 3krpm max, and changing your oil filter every 1000 miles. Otherwise change it sooner. j/k

Also 3K is recommended for any non-synthetic oil. Semi-synthetics and full synthetics range from 5K-15K depending on driving style. Here's my 2 cents on synthetic-Mobile 1 that you buy at Wal-mart or Auto Zone is NOT the same grade that Porsche came with. Most cars That I have delt with that had Mobile 1 in it showed extreme wear on the valve train(Cam specifically) Products like Amsoil, Royal Purple and Lucus are top grade synthetics that will protect you engine and last the 15K

I wouldn't put anything thinner than a 15w40 in my 944, Comma do a 15w40 semi synthetic called XT2000.

I've been a Mobile 1 type of guy for my Grand Prix since day one, and it's not treated me badly at all. Of course the car has only 25K miles on it, so it's probably too early to tell.

I dont know if anyone really cares but I just got to watch my 944 burn to th ground because it took the fire dept. 20 mins. to go a 1/4 mile up the street to put my car out.
real bummer I had so many plans for my baby.

Sorry to hear that. Must have been a really traumatic event for you. Hope that you are doing better these days.

RIP 944, DONT WORRY, its gone to a place much better. Sorry mate.

Probably a sensitive subject-but how in the world did you manage to cook a 944?

yeah, what happened?

RIP

I'm particularly interested as I'd want to prevent it from happening to me. I'm sure that others would like to know as well.

Ouch, that's sad to hear.

I bought the 944 with 175,000 miles it, and I don't know which type of motor oils have previously been used. I plan on switching over to Mobile-1 when I have a lube, oil change, oil filter change performed at the next service.

I've heard that Mobile-1 is a high detergent oil, and could very well loosen up all the accumulated 'crud' in the lower 1/2 of the engine. This would probably choke the new oil filter. Best to clean it out first. When I asked the mechanic how to clean out the gunk before switching to Mobile-1, he said that a good procedure would be:
Put 2 quarts of ATF and then fill the rest with some crap motor oil Drive very gingerly for 5 miles Drain the old oil out Replace with Mobile-1 and a new oil filterI have to admit that I've never heard of such a procedure, but it would appear to make some sense to me. From what I understand, the ATF is a very high detergent oil, and would really clean out the engine's innards. It would also seem to me that a short 5 miles driving gingerly with that mix of stuff in the engine shouldn't damage anything. What do you guys think?

When I asked the mechanic how to clean out the gunk before switching to Mobile-1, he said that a good procedure would be:
Put 2 quarts of ATF and then fill the rest with some crap motor oil Drive very gingerly for 5 miles Drain the old oil out Replace with Mobile-1 and a new oil filterI have to admit that I've never heard of such a procedure, but it would appear to make some sense to me. From what I understand, the ATF is a very high detergent oil, and would really clean out the engine's innards. It would also seem to me that a short 5 miles driving gingerly with that mix of stuff in the engine shouldn't damage anything. What do you guys think?

engine flushes are an emotive subject to a lot of people! if you're happy using them and know the repercussions then they are fine.

Umm. What sort of repercussions am I looking at?

Could the flush mixture damage the seals? The bearings? The lifters? The valve guides? The oil pump?

Umm. What sort of repercussions am I looking at?

Could the flush mixture damage the seals? The bearings? The lifters? The valve guides? The oil pump?

a little bit of everything. if an engine's never been flushed before you'll have varnish and gunk all over the internals of the engine. removing it will increase your tolerance's / show up leaks that you didn't know you had / etc.

i'm not against using a flushing agent, you just need to be aware of what they do.

if an engine's got a history of having a flushing agent used on it regularly, then this isn't an issue. but on a 175k mile engine that's never had it done before you never know what's going to happen.

i've never heard of atf being used as a flushing agent though. it might be that atf is milder than the off the shelf flushing agents, and is only being used to make sure you remove all the old mineral oil ready for your nice new mobil-1?

Given this information, I'm inclined not to flush the engine and just put Mobile-1 in with a new filter. If the Mobile-1 is a higher detergent oil, then it'll remove some of the old mineral oil deposits as it goes along. I guess I should figure a quick oil/filter change with Mobile-1 soon thereafter (like 100 miles or something) to get the loosened and filtered deposits out of the engine. Seems to me that switching to Mobile-1 is going to do what the flush would, except perhaps to a lesser extent.

The downside of continuing the regular mineral oil that I can see could be limited oil volume to the various parts of the engine due to deposits in the oil passages. This is not good, as I plan to run the car pretty hard during the local PCA's drivers education events (the reason that I bought the car in the first place).

Is there anyway to test the oil that's in the car right now to determine which oil it is? Syntheic or mineral? This would be a piece of information that would complete the puzzle.

Thats a bit odd, as i thought ATF as a flushing agent was common in the states, as i have read a few wright ups and they was all from the states and had all said use ATF. I know MERCEDES dealers use it.

Given this information, I'm inclined not to flush the engine and just put Mobile-1 in with a new filter. If the Mobile-1 is a higher detergent oil, then it'll remove some of the old mineral oil deposits as it goes along. I guess I should figure a quick oil/filter change with Mobile-1 soon thereafter (like 100 miles or something) to get the loosened and filtered deposits out of the engine. Seems to me that switching to Mobile-1 is going to do what the flush would, except perhaps to a lesser extent.

that's the same conclusion i came to for my turbo 944. :)

The downside of continuing the regular mineral oil that I can see could be limited oil volume to the various parts of the engine due to deposits in the oil passages. This is not good, as I plan to run the car pretty hard during the local PCA's drivers education events (the reason that I bought the car in the first place).

as long as you let the car warm up first (remember the oil takes a lot longer to warm up than the water does) you shouldn't have any problems.

i'd do two changes as you suggested. i know it's really hard (escecially if you've only just bought the car) but go easy on it for the first couple of hundred miles after the 1st change, then do an oil and filter change and you can start to enjoy yourself then.

Is there anyway to test the oil that's in the car right now to determine which oil it is? Syntheic or mineral? This would be a piece of information that would complete the puzzle.

sadly no, i've asked several petrochemists that same question. also there are rules for what makes an oil allowed to be called synthetic, but they aren't as obvious as you would think. merely adding a few of the right sort of additives to a mineral oil will allow you to market it as being synthetic.

Thats a bit odd, as i thought ATF as a flushing agent was common in the states, as i have read a few right ups and they was all from the states and had all said use ATF. I know MERCEDES dealers use it.

it's possible, i'm from the UK :) automatics aren't as common here so it's easier to get hold of something sold as a flushing agent rather than using something else as a flushing agent.

Well, I'm certainly glad to have hashed with through with all of you. My experience has been that bouncing ideas off of other knowledgeable people generally contributes to the best possible decisions being made (something about the cumulative IQ of the group exceeding any individuals). Thanks for the help.

WRT: Taking it easy, that's not a problem. I'll not be able to get to the track for drivers ed. until May next year. The car goes into storage 12/1, and will come out of storage 4/1, so there's a fair amount of street driving yet to be done!

The first oil change is scheduled for this weekend, and I figure another one shortly before storage, so I'll be able to get all the gunk out properly.

i'm glad you found any of my info useful. :iceslolan

my turbo is in storage now too. :( but i still use the 924 as my daily driver. :)

whilst you have the s2 parked up, i'd recommend starting the engine once a month and letting it run untill it's warmed up. i also give the foot break a bit of excercise to make sure the callipers don't seize. also release and engage the handbrake (emergency brake in the US?) a few times too.

I have a feeling that I'll all right regardless of what I'm going to do. I just checked the maintenance history and noticed that at 165,000 (5/19/2000) the following items were taken care of:

Water Pump Belt, timing belt, Oil Seals
Water Pump Replaced
Timing Belt
Balance Shaft Belt
WP Gasket
Crank Shaft Seal
Crank Shaft Seal bushing
Balance Shaft Seal Kit
Timing Belt Tension Pulley

So it would seem to me that all the important engine seals are still pretty new. I'll bet that I could even do a power engine flush, like at Uncle Ed's, and still be OK as far as the oil leaking is concerned. Just don't want to impact the engine's compression.

WRT storage: I plan on: Full tank of premium with octane stabilizer Putting a squirt of engine oil in each cylinder and turning it over a few times to coat the cylinder walls Putting it up on blocks to unload the tires, but not the suspension (blocks under the suspension so it's not hanging in an unnatural fashion) Removing the battery Mothballing the engine compartment (perhaps, it's in a garage) Covering the exhaust pipe with a can to keep rodents out Thanks for the hint about the brakes. That's probably a really good idea.I'm thinking that in the spring I'll unblock it, roll it outside the garage, put the battery back in and fire it up again. It'll smoke a bit until the cylinder oil is burned off, but that shouldn't be much.

I think you're f--in' crazy! 944 all ready have a bad rap for loosing rod bearings I wouldn't give it any excuse do it to you. Also remember this is a Porsche not a buick, there shouldn't be any crud in the engine anyway. My 2 cents-a a car with 175K on it you shouldn't be using Mobile 1 anyway. Its only asking for trouble(leaky seals, worn bearing, low pressure). Use a quality brand 20/50 for summer driving and a 10/40 for colder driving.

Use a quality brand 20/50 for summer driving and a 10/40 for colder driving.
What do you consider a "Quality Brand"?
I'm just curious to know what everybody thinks of me running Castrol GTX 20W50 from Happy's Discount Oil Parts Store.....

Well, OK. I could see where a Porsche engine would not build up as much gunk in the oil as say a Detroit engine would.

But I'd still very much want to run Mobile-1 in it, as I will be driving the car hard on the track during the local Porsche club's drivers education events.

everything you've ever wanted to know about oils...

http://www.xpower-mg.com/Motor_Oil_FA_Questions.htm

my 944 turbo se with ~165k is using fully synth 15w50 mobil 1 with no problems. as long as you stick to the weight recommended in the handbook, you shouldn't have any problems.

My choice of a quality non-synthetic would be valoline/havoline/castrol-I havn't had good luck with penzoil-mobile. If your car always had synthetic oil then stick with it. but if it hasn't you're setting your self up for oil leaks and engine problems. I personally just don't like Mobile 1. I've seen too many engines come through the shop with bad cams, worn out valve train and spun bearings and 90% of them had Mobile 1. I personally use Amsoil senthetic in everything that I own (towing equipment, motorcycles, 930, 944S, But I've used this since they were new. Do the research, check the web sites. If after that you're convinced its the best choice then go for it.

i'm aware that a lot of things are called somthing different on the other side of the pond, but i've been assuming that everyone who's been saying mobile-1 has meant mobil-1 (no e). is this true or have people been talking about a different product?

Umm, I think that EU Mobil is the same as American Mobile-1, or I'm not spelling the name correctly.

these are the people i'm talking about, are they the same in the US?

http://www.mobil.com

yup.

My $.02. 15 years ago my father started using Mobil 1 in his 62 Ghia after it's 2nd rebuild. The little 1.6 liter air cooled VW engine with an oil operating temp of 250-300 was still running stong after going 180,000 miles. When it became mine, I used the same brand oils and the same brand filters he did. I put 68,000 miles on the car before beginning the restoration project. When i disassembled the engine, I expected to find old worn out parts. Not true. I found no scoring anywhere, polished surfaces with very little wear, and even the bearings were almost reusable.

Thats because is german, qualitys the word your looking for!

ooh, that explains it then!

I remember when I used to see "Pump Top" advertisments for Mobil 1 at their filling station. They probably still have them, I'm just not aware of seeing this recently.

Anyway, while filling some 50 gallons into a servicetruck I was driving at the time..... I looked real hard at the photo's. It was a comparison campaign showing what the inside of your oil pan looks like with mineral oil/compared to Mobil ONE.

Being the idiot-savant that I am refered to by my closest family, I became aware of minor scratches and flaws in the flanges of the oil pan. Gasket material that hadnt been removed from the filthy, inferior, Dino-Oil soiled belly pan.

Then looking at the sparkeling clean Mobil ONE oil pan with envy. I NEED SOME OF THIS! Thats rocket science at work there!
But Wait..... hey, thats the same gasket stain, scratch, what the???? They just cleaned the same oil pan and put clean oil in it.... Where's the truth in advertising? Those Bastards!

Had they not tried to BS me, I might have tried their product. I hear good things and some other then good things..... I dont think I suggest Mobil ONE gear oil. Somethings not quite right with it... so I hear.

If your ever in a Mobil station, look for that poster, I bet they still use it.