depends on the specifics. if- in driving very little- you take mostly short trips where the engine oil can’t get up to full operating temperature, then contaminants can build up and water can begin to collect (since one of the two main products of hydrocarbon combustion is water.)
BMW recommends 15,000 mile intervals using synthetic oil. The computer in a 3-series will start prompting you when you’ve used 550 gallons of fuel, which is about 15k easy miles. If you’re running the car hard enough to use that much fuel more quickly, they figure you probably need to change the oil ahead of schedule.
What the geeks on car forums do is send samples to Blackstone Labs and have it analyzed for about $25. So many have had no problems with their oil after 15k that I don’t worry about it.
Also a big source of water in a rarely driven car is humidity. The heating/cooling cycle of using the engine and day/night weather draws air in. As the air cools water condenses out and can end up in the oil.
You are right and a little wrong IMHO. The 3k thing with regular oil makes some sense during the first 10-12k but after that, even back into the 40s models, 5k is more in tune with reality. Yes, what most makers call severe is what we would call normal but they are also dealing with avoiding any risk at all of warranty work and/or unhappy customers. And even with the closer tolerances we have today, a motor is settled in enough that 5k on normal oil is fine; especially once you crack the 25k mark. In a place like Pittsburgh PA you will get more wear from not changing your oil to match the season than you will from the difference between 3 and 5k. I don’t bother with that “winter weight” thing either as a rule.
Now ----- car makers are not stupid. They know us and our habits. If they say 3k, we may get to it by around 5k. If they said 5k some of us would wait for 10. So that 3k thing plus honoring the terms of the warranty keeps us a little more in line and saves them money for repairs down the road.
Me? New motor/new car and I’ll go 3 for a while and then 5 and synthetic oil once it hits 100k or so. Its worked well for me on four different cars since 1991. But appropriately since we are talking about cars ------- YMMV.
Okay, then with rough driving, my manufacturer recommends 5000. And I agree with kopek, - manufacturers are intentionally being conservative, as it’s probably fine to change in longer intervals. But never does that interval even approach 3000.
There is no good reason to change every 3000, except to support a Jiffy Lube.
Mine seems to have called for it around every 10k miles, and says 10k to next service just after. I’m fairly easy on cars in terms of driving personality for the most part and mix of driving has averaged around 28mpg so it’s more like 350 gal of gas between oil changes. It’s just finishing up warranty, during which period I’m not going to second guess the condition monitor or the oil the BMW dealership puts in under the ‘free’ maintenance plan. Once it’s on my dime I’ll have to pay attention to choosing the right oil and eventually if I keep the car a long time more of a chance the monitor gets screwed up. But just changing the oil more frequently according to old conventions, I don’t think so.
And this is true with more cars now. It’s no longer even parsing the wording in a manual as to what is ‘severe’, what’s ‘extensive’ idling etc., it’s what the car says.
Also any conversation on the web about car maintenance naturally draws a disproportionate sample including the generally fairly rare people who keep cars up to huge mileages who could possibly afford not to. Most people trade cars in at a point where even if there is some small difference in wear depending on exact maintenance procedure, they get no credit for that on the trade in price, and the chance of the car actually crapping out because of it is minuscule.
:eek: $70 for an oil change? I can get mine done here for under $20, which is cheaper than I can buy 5 quarts of oil and a filter to DIY. It includes nothing but the oil and filter change - no “15,000 point check and top off other fluids” like some places, as I take care of that. If I went with synthetic it would cost about $30. Otherwise I would go back to changing my own.
I get that not everyone can or wants to change their own oil, but that price gave me sticker shock.
Ultimately the genesis of the 3k oil change was likely that it was the most common one that most drivers ran into (all my cars have had a 5-6k normal interval and a 3k “severe” interval, with my normal driving always falling into the “severe” category), and the quick-lube places clamped onto it because it’s short and coincides pretty closely with quarterly oil changes for most people. That was in the early-mid 1980s I think, when the quick-lube places became popular.
Fast forward 30 years, and oils have become MUCH better in all respects. The base stocks are considerably better, being mostly either entirely synthetic PAO/ester/POE/GTL oils, or petroleum basestocks that have been hydrotreated to a greater or lesser degree (all much better than old-style refined). The additives have become much better as well.
So the general rule these days is that “conventional” oil is probably good for 5k-6k under all conditions, and today’s synthetics are good for 10k in most circumstances, even if your manual says your OCI is 3k
My '17 Jeep is spec’d for 5000 miles. When I took it in to the dealer for the first change they advised me to just wait for the oil warning to schedule the next change. Since they’re the ones I would be paying for the change they were basically delaying that income so that lends credibility to the advice. When I asked why they said the onboard computer calculates when the oil needs changing based on my driving.
My second change was 8000 miles later. Haven’t gotten to the third yet.
Hi there, I make engine oils. Actually, I’m the guy responsible for engine oil blend quality at a place that makes the chemicals that go into the engine oils which oil suppliers sell, but whatev.
Anyway, you need to change your engine oil when the overbase from the detergent in the additive package has been used up. Modern oils – synthetic or otherwise – no longer break down fast enough to be the limiting factor. Other additives – dispersants, antioxidants, viscosity index improvers, etc. – are present in sufficient quantity that they are not limiting, either. The most common route for oil breakdown producing acidic byproducts is water in your crankcase, but there’s lots of other routes too.
Modern additive packages have higher treat rates for overbased components, so they can last longer. And as I said, modern oil blends last longer, too. Hence the longer change interval. If you’re using a low-grade engine oil, or your car has “severe conditions” that would accelerate oil breakdown, change more often.