Oil Change Intervals

Factual Questions
1

Took my car in for its 20,000 mile inspection and got the works done on it, tire rotation, lube this, lube that, etc. Also the oil and filter were changed. Got the car back and noticed as I was driving off they placed that little oil change sticker reminder on the windshield. By the dealership’s estimate I was supposed to come back in the next three months or 3,750 miles, whichever comes first. Now I have had this car for two years now and have only had the oil changed twice. Once every 10,000 miles, like the owner’s manual states.

So whose schedule should I follow? The owner’s manual or the dealership’s? And why aren’t the dealership and the auto maker on the same page when it comes to maintenance schedules?

2

First off, the dealer’s undoubtedly out to make money.

Second, it might be just a standard estimate without checking the car’s make too closely–100% of the cars I’ve owned/driven have recommended a 3,000mi/3mo oil change interval.

Third, what the heck are you driving that the manual recommends a 10k mi oil change interval?

3

What kind of car do you have?

4

It is a 2004 Honda Accord.

The owner’s manual has, for normal driving conditions, an oil change schedule of every 10,000 miles or once every year.

5

My BMW runs on synthetic oil, and the factory-recommended oil change interval is 15,000 miles. Porsche, Mercedes, and maybe Audi have similar recommendations - Porsche may even be as high as 20,000.

I change it every 7,500, because I figure it’s cheap insurance, but plenty of people go with the 15K interval with no problems.

6

Go with the owner’s manual, as long as you are using the recommended oil as well. Synthetic oils can last that long, conventional oils cannot.

If it turns out that the dealer used conventional oil, then a 3750-mile interval makes sense. However, running conventional oil in an engine designed for synthetic is not a good idea (and yours likely is). If that’s the case, I would go back to the dealer and demand that they give you another oil change, with the proper stuff this time, for free.

7

Also, if the dealer did use synthetic oil, then the 3,750 mile change interval is pure and simple bullshit. It is actually bad for your engine - studies have shown that synthetic oils actually require a few thousand miles to “break-in” before they begin to function optimally, meaning that changing your synthetic oil too often results in undue wear on the engine.

8

I would say that you should follow the mfgrs. recommendations, including the grade of oil. There is another factor though, your driving habits. Generally, if you do frequent short trips, say 5 miles or less and the car then sits for more than 20-30 minutes between trips, this causes condensation buildup inside the engine. Water plus hydocarbons results in acid formations, degrading the oil. This type of driving requires more frequent changes, perhaps by as much as half the recommended interval. Other factors that reduce the interval might be driving in high dust areas, dirt roads, off road, construction areas, or even lots of stop/start city driving.
ITOH if you do lots of highway driving, where the engine operates at fairly steady rpm’s for long periods, you might even extend the changes by 10 to 25%, although I’d probably still not exceed the recommendations, for warranty purposes.
I’m wary of these oil change businesses. Obviously most of them are legitimate, but even then they often try to sell you products and services that you don’t need. There are also incidents where they do nothing and charge you anyway and also where mistakes are made. I would suggest that you have them pull the dipstick and show you that the oil is clean and at the proper level before driving away, and also check the ground after the first time you park. There have been instances where they forgot to add the new oil, misjudged the capacity (overfilling can be as bad as no oil), or mistightened drain plugs or filters.

9

I’ve had only one bad experience with one of these places, and that was about 20 years ago. Apparently, when they changed the oil filter they left the old gasket in place, as well as the new gasket. I drove less than 2 miles, and my oil light came on, so I immediately hightailed it back there. All of the oil had leaked out between the two gaskets.

They were very apologetic and not only fixed the problem, but paid to have my engine steam cleaned at a different shop, because oil had sprayed all over the place.

10

According to my information, the factory recommended intervals are as follows:

4 cylinder, normal service: 10,000 miles.
4 cylinder, severe service: 5,000 miles.
6 cylinder, normal service: 7,500 miles.
6 cylinder, severe service: 3,750 miles.

Severe service includes driving mainly under one or more of the following conditions:

Driving less than 5 miles (8 km) per trip or in freezing temperatures.*
Driving less than 10 miles (16 km) per trip.*
Driving in hot [over 9O°F (32°C)] conditions.
Extensive idling or long periods of stop-and-go driving.

For many people, this is consistent with typical city driving. Most auto shops in metropolitan areas assume severe service in their oil change interval recommendations. The question is (if my info is correct), why are they saying 3,750 miles instead of 5,000 miles?

My guess would be the dealer is using the 3,750 mile interval because it was the norm (for most Japanese cars) for many years. Since it still applies to some models, they’re probably taking the easy way out and using a “one size fits all” approach rather than dealing with different intervals for different models/engines.

I think you’ll be fine following the manufacturer’s recommendation. They invest a lot in developing and researching these things, and are an authoritative source. Dealers seldom have a sound technical reason to suggest otherwise.**

*These two taken together don’t really make sense. If it said trips of less than 5 miles, and trips of less than 10 miles in (not or in) freezing temperatures, it would make sense.

**Seldom, but I wouldn’t say never. There have been cases where real-life experience shows that the factory recommended interval and/or oil type is not sufficient to protect the engine. I’m not aware of any such situation with Honda, however.

11

Says who? You know something the car manufacturers don’t?

This car does not specify synthetic oil.

12

Jeesh! What the heck kind of wierd cars do you drive?

13

I would like a cite for synthetic oils lasting longer than conventional ones at normal operating temperatures (below 275 fahrenheit).
I’ve been studying this topic for years, and I can’t find a good cite for that assertion, despite quite some time spent looking.
The failure mode of most crankcase oils is additive depletion, not the base oil failing. Typically the anti-acid adds fails, and the oil goes acidic.
This means that a conventional oil with a high-quality additive pack has the same endurance as a synthetic oil with the same quality of additive pack.

Every synthetic I’ve ever researched has what appears be a high-quality add pack. While many conventional passenger car motor oils do not, some are better than others, and it appears that diesel-oriented motor oils like Shell Rotella T have the same kind of heavy-duty additive loadouts that synthetics get.

In answer to the OP: if your manual says 10,000 miles in your driving conditions then feel free to run 10,000 miles. Honda has its own specification for 5W20 motor oils to meet (harsher than Ford’s, which is the other 5W20 pusher), and if the oil used in your vehicle is compliant with that spec you should be fine.
Incidentally, by the standards of a few years back, every name brand 5W20 is synthetic. The cheapest base oils you can mix in to create an oil that will meet the manufacturer specs for 5W20 are Group III, which means they’re very highly refined petroleum oils. By today’s standards, they’re basically all synthetic blends or better.
Make sure there isn’t a “gotcha” in the manual that trims your oil change interval back to 5,000 miles or so if you drive in town all the time, etc etc.

14

What’s the recommendation if your driving is a mix? Two miles each way to the train station on week days, but 100+ mile trips on weekends? Are the long weekend drives enough to “cook” the bad stuff out?

And 5w20? How long before we’re just lubing our engines with water?

15

There is no official recommendation that I know of. Even the given intervals are somewhat arbitrary, being round numbers. You pretty much have to try to “common sense” it out.

Well, water’s not quite as slippery as oil. :wink:

The trend over the past couple decades has been to lower viscosity numbers. Various additives and such can enable the oil to protect as well as – probably even better than – the thicker oil that was previously more popular. The lower number stuff flows better, and getting it where it needs to be quickly seems to help a great deal.

16

I’m thinking we’ll be running 5W20 untill we run out of petroleum.
I don’t expect you’ll see 0W10, 5W10 or 10W10 on store shelves.
I read a study comparing wear rates with different viscosities. I seem to recall it having been compaing a number of different oils with an eye towards “what is the most fuel-efficient oil we can run without grenading our engines.”
Supposedly wear rates skyrocket once you get to a viscosity slightly below 20 weight.

17

If you’re a fan of Car Talk, they recommend every 5000 miles. My '97 Aerostar recommends every 7500, but I’ve changed every 5K since I got it, and at 171K miles with no major engine problems, I can offer it anecdotally as a good interval.

Plus it’s easy to remember - multiples of 5K is easier math than multiples of 3750 or 7500 or 4283 or whatever…

18

Like so many things “It all depends.”

Petroleum Oils & Filter 3,000 to 6,000 Miles. Remove products of oxidation etc. from
oil and provide for good filtration of the new oil.

Synthetic Oils & Filter 7,500 to 15,000 Miles. Same reasons.

19

Would a car maker’s spec be a good enough cite for you?
I was just looking at oil change criteria the other day (don’t I lead an exciting life?)
Anyway several of our engines have a different service interval depending on the market. In Europe the interval is 30,000km using 0W-30 oil meeting ACEA specification A5/B5. The same engine here in the states has a 12,000km service interval using 5W-30 meeting ACEA spec A1/B1, and or API SL.
Here in the US to the best of my knowledge the only oils that meet ACEA A5/B5 are full synthetic oils. The last time I went oil label reading (I told you I lead an exciting life!) no dinosaur based oil met the A5/B5 certification.
So is it the base oil quality or the additive package that makes the oil go from A1/B1 to A5/B5? Beats me, but the only oils you can get on this side of the pond that meet the A5/B5 are synthetic.
Getting back to the OP, I would pay very close attention to the quality of the oil being used in the oil change. If the dealer is using an inferior grade of oil (possible) it does not matter that the weight is correct, engine damage can occur.

API grade info (PDF!)
Here is a chart of ACEA grades

20

Rick,

Your actions in the fight against ignorance are admirable. While you marshal evidence against my position, you don’t exaggerate what said evidence implies. I applaud you for that.
The auto maker’s oil change interval reccomendations will not wholly satisfy me, though they do provide something for me to consider.
The reason that they will not satisfy me is that the reccomendations are based on both technical and non-technical criteria. If the carmaker in question was doing everything on the basis of technical results, I cannot imagine the reason for reccomending A5 0W30 in Europe and A1 or SL 5W30 here. “Europe” and “US” are both basically extremely broad geographical zones, and it seems that they would grab the same specs if the specs were handed out sanely. Now if it was Japan or Australia versus Canada, I could see different standards…
Incidentally, you won’t find an A5 0W30 that’s non-synthetic because of the viscosity spread. It appears to be impossible to produce a 0W30 that isn’t synthetic. That’s fair, given that flowing at -45 and still lubricating well requires quite a deal of versatility on an oil’s part.
I seem to recall that there are some semi-synths that meet the A3 long-length spec. One of them, Federated Auto Parts 10W40, sells for $2.09 per quart, in fact. [1] That price point would usually be associated with a premium full-conventional oil or low-to-mid-grade synthetic blend.
Good point though, really.
Can a fully conventional oil meet A3/etc?
Hard to tell, although we know that some oils that are around 85% conventional can. Hard to tell what really goes into most oils without deciphering maker MSDS. Many blenders consider how conventional their synthetics, blends and conventional oils are to be a state secret.
[1] http://www.midwayautosupply.com//detailedproductdescription.asp?1332
[2] Note the Castrol GTX 10W40 at this site, which appears to meet A3. GTX is Castrol’s conventional brand. http://www.motor-world.co.uk/kroozin/category.php?sub_cat_id=39
[3] Schaeffer’s Synthetic Blend 10W30 meets A3. http://www.schaefferoil.com/datapdf/703.pdf [PDF]