Oil Change Frequency
08-30-2010, 05:23 PM
#16
Rennlist Member
LiBr: My mistake; b. should have read " ... longer service interval ...."
Reminds me of when students found errors in my m-c questions. Fortunately for all, I'm retired now.
Reminds me of when students found errors in my m-c questions. Fortunately for all, I'm retired now.
08-30-2010, 06:48 PM
#18
Drifting
The folks that fill up every 3-5k miles kill me. "Just being safe." Do you stop and fill your gas tank every time it gets half empty, just to be safe? Imagine stopping with your tank half full, dumping out all the remaining gas and then filling up completely - would you consider that "just being safe"? After all, some of the remaining gas could be bad.
Modern synthetic oils are designed to be changed every 10-20k miles, not 3-5k. Spend your money how you wish, but don't fool yourself into thinking you're doing anything other than being wasteful with it.
Modern synthetic oils are designed to be changed every 10-20k miles, not 3-5k. Spend your money how you wish, but don't fool yourself into thinking you're doing anything other than being wasteful with it.
I bought into some of the hype and dumped my oil early. Unlike most, though, I sent in a sample for testing. Blackstone said my oil at 12k miles was just fine despite me racing this car, and recommended I try 13k next time.
Moral of the story: If in doubt, take an oil sample and send it in for testing. You may be dumping perfectly good oil this time, but no sense doing it again!
08-30-2010, 08:11 PM
#19
Rennlist Member
If people want to throw money away dumping perfectly good oil, that's their prerogative... it's when they start trying to convince others to do it that's a problem. Do any of you who are changing your oil at less than Porsche's recommended intervals have any oil analysis or anything else to back up your claims, or just anecdotes and conjecture?
I bought into some of the hype and dumped my oil early. Unlike most, though, I sent in a sample for testing. Blackstone said my oil at 12k miles was just fine despite me racing this car, and recommended I try 13k next time.
Moral of the story: If in doubt, take an oil sample and send it in for testing. You may be dumping perfectly good oil this time, but no sense doing it again!
I bought into some of the hype and dumped my oil early. Unlike most, though, I sent in a sample for testing. Blackstone said my oil at 12k miles was just fine despite me racing this car, and recommended I try 13k next time.
Moral of the story: If in doubt, take an oil sample and send it in for testing. You may be dumping perfectly good oil this time, but no sense doing it again!
08-30-2010, 08:28 PM
#20
Rennlist Member
Oil discussion thread in CGT forum where Doug educates
Link to oil reports by Doug in same thread
Doug educates
Doug educates again
Doug educates again
Doug educates one more time
Synthetic oil life study
The bottom line is that a lot of people who are smarter than me (and not armchair quarterbacks) say its okay to skip the 3k oil changes.
08-30-2010, 08:55 PM
#21
Race Director
08-30-2010, 09:04 PM
#22
Racer
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Why I change my oil every 5k miles:
1. I like to do it at regular intervals, and not have to worry about one oil change being based on years and the next on miles. That would have a loss of symmetry I find disturbing.
2. An oil change costs 0.17% of what I paid for the car.
3. The oil looks dirty when it comes out.
4. With 3 cars, setting each at a 5k interval is the only way I can keep track of what needs to be done, to which car, and when.
5. I'm a moron.
6. If I had leased the car, I would change the oil every 10k-20k, if at all.
7. The car feels like it runs smoother after the oil is changed.
8. I want to show that these synthetic dinosaurs did not die in vain.
9. I'm supporting the economy when nobody else is.
10. This is trite, but it's important: It's. My. Car.
1. I like to do it at regular intervals, and not have to worry about one oil change being based on years and the next on miles. That would have a loss of symmetry I find disturbing.
2. An oil change costs 0.17% of what I paid for the car.
3. The oil looks dirty when it comes out.
4. With 3 cars, setting each at a 5k interval is the only way I can keep track of what needs to be done, to which car, and when.
5. I'm a moron.
6. If I had leased the car, I would change the oil every 10k-20k, if at all.
7. The car feels like it runs smoother after the oil is changed.
8. I want to show that these synthetic dinosaurs did not die in vain.
9. I'm supporting the economy when nobody else is.
10. This is trite, but it's important: It's. My. Car.
08-30-2010, 09:10 PM
#23
Rennlist Member
Wow, thanks for the links. I hadn't encountered those threads and you're right -- Doug sure does know about lubricants. Great reading.
08-30-2010, 09:20 PM
#24
Race Director
If people want to throw money away dumping perfectly good oil, that's their prerogative... it's when they start trying to convince others to do it that's a problem. Do any of you who are changing your oil at less than Porsche's recommended intervals have any oil analysis or anything else to back up your claims, or just anecdotes and conjecture?
I bought into some of the hype and dumped my oil early. Unlike most, though, I sent in a sample for testing. Blackstone said my oil at 12k miles was just fine despite me racing this car, and recommended I try 13k next time.
Moral of the story: If in doubt, take an oil sample and send it in for testing. You may be dumping perfectly good oil this time, but no sense doing it again!
I bought into some of the hype and dumped my oil early. Unlike most, though, I sent in a sample for testing. Blackstone said my oil at 12k miles was just fine despite me racing this car, and recommended I try 13k next time.
Moral of the story: If in doubt, take an oil sample and send it in for testing. You may be dumping perfectly good oil this time, but no sense doing it again!
Since high levels of water combines with other combustion byproducts to form acid and because water in oil lowers its viscosity and increased its tendency to foam/aerate -- neither of which is any good for an engine's continued good health -- I decided that 5K miles would be plenty long enough to keep the oil in the engine.
When I had the oil analyzed I spoke with the people at the place that did the analysis. The place specialized in big rig servicing. I was told about half the big rig owners do the oil analysis thing the other half just change the oil every month or so, or after about 30K miles. Some trucks many run longer now between oil changes, this was circa 2002.
The proper procedure is to remove the oil filter housing, pour out some oil for analysis then analyze the oil. This place did it on site. If the oil ok the filter is replaced and the filter housing replaced. If the oil not ok the oil is changed.
Even if the oil is ok -- since this shop doesn't do oil changes for Porsches and I wouldn't want it to anyway -- I have to have the tech replace the filter element, the o-ring, reinstall the oil filter housing and then drive the car home and arrange to change the oil at my convenience. Another filter element and another o-ring and a half a quart or so of oil wasted.
Plus it takes time.
Then one has to think when the next analysis is due. Maybe the oil's deteriotation is not linear? So if the oil is ok at 4K miles when do I test again? 5K? 8K?
To me I would just rather pick a number of miles and change the oil.
I have better things to do with my time than to extract oil from my cars' engines and send the oil out for analysis.
I probably dispose of oil that has some life left in it. I don't care. My goal is to extend the life of my cars engines at the expense of some relatively cheap oil rather than shorten the life of my cars' engines to save some money on oil changes.
As I've mentioned before, I've come across many stories of car owners -- over the years -- discussing their cars' extreme longevity. I have yet to come across one that claimed to have changed the oil every 15K miles (Porsche's schedule for my 02 Boxster). Most change between 2K and 5K miles. 2K miles a bit extreme but some of these car owners are driving cars with carbs and poor crankcase ventilation and water and unburned fuel build up very bad in a very short time. Also, some have high lift cams, and other engine mods that place an even higher demand on the oil.
If you want to run your oil longer, whatever number you want is up to you.
When your car's engine reaches 234K miles following 10K or 12K or 15K mile oil change intervals I want to know about it. Until then I'll stick with my 5K mile oil changes.
Sincerely,
Macster.
08-30-2010, 11:47 PM
#26
Three Wheelin'
Join Date: Jan 2007
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Why was the recommended service interval changed from 20k miles/2 years to 12k miles/1 year?
a. The way the new cars were built called for a shorter service interval.
b. They found that the longer service interval resulted in excessive wear.
c. New buyers were attracted to the longer service interval (marketing ploy).
d. Dealers were attracted to the shorter service interval (dealer profit ploy).
e. None of the above.
a. The way the new cars were built called for a shorter service interval.
b. They found that the longer service interval resulted in excessive wear.
c. New buyers were attracted to the longer service interval (marketing ploy).
d. Dealers were attracted to the shorter service interval (dealer profit ploy).
e. None of the above.
Dealers were squawking to Porsche about the loss of revenue from the extended maintenance intervals.
Porsche tells me to change every 20,000 miles. I do it at 10,000. Anything more is overkill. Perhaps I'll send a sample to Blackstone Labs next time...
08-31-2010, 12:21 AM
#27
Rennlist Member
I hate when folks like that move on because the knowledge, while stored in the forum if you know where/what to look for, seems to fade away.
08-31-2010, 01:25 AM
#28
Nordschleife Master
Well done ... knowledge over ignorance always wins ... 
I couldn't find the link to where he worked (at least, I didn't see it while skimming), but the guy is/was Doug Hillary.
Looks like his last post was July '09 which is sad, as he was a wealth of info. For your reading pleasure...
Oil discussion thread in CGT forum where Doug educates
Link to oil reports by Doug in same thread
Doug educates
Doug educates again
Doug educates again
Doug educates one more time
Synthetic oil life study
The bottom line is that a lot of people who are smarter than me (and not armchair quarterbacks) say its okay to skip the 3k oil changes.
Looks like his last post was July '09 which is sad, as he was a wealth of info. For your reading pleasure...
Oil discussion thread in CGT forum where Doug educates
Link to oil reports by Doug in same thread
Doug educates
Doug educates again
Doug educates again
Doug educates one more time
Synthetic oil life study
The bottom line is that a lot of people who are smarter than me (and not armchair quarterbacks) say its okay to skip the 3k oil changes.
08-31-2010, 03:20 AM
#29
The way I rationalize my experience is that if the oil is not doing its job then there will be more wear on the engine which, in turn, will increase oil consumption. Since I have added only 0.5 quart of oil in 55 K miles (and that was early on) and I have not seen ANY evidence of increased consumption I'm going to assume that engine wear is not excessive and thus that the oil change interval I have chosen is appropriate.
I hate it when people waste money and resources for stupid reasons.
I hate it when people waste money and resources for stupid reasons.
08-31-2010, 10:03 AM
#30
Rennlist Member
See, I don't care if someone wastes their money. It bugs me when they waste their money and have convinced themselves it is not a waste. I know fully well I'm wasting money on a 911 vs. an Accord when my daily commute is a 4 mile round trip to daycare, but I'm happy to waste it. 