Oil change intervals?

Modern synthetic oils can run much longer before the base oils break down. However, they can't keep any more blowby debris in solution than old oils, and the viscosity improvers don't last any longer.

So... whether you can get away with extended oil change intervals with modern synthetics on older engines depends entirely on what characteristic of the oil is limiting the oil lifespan.

And you can't really tell that without doing regular oil testing on a constant basis. This is very expensive, much more so than just changing your oil a lot.

So, the answer is that it depends. But I'll say that I have been using synthetic oils with 3,000 mile changes for the past 20 years and I have

--scott

If there is significant blowby debris, then the car will be using oil.

And the rings aren't doing their job.

Full Synthetics are good for at least 10K when used with the right filter.

Andy

Today's longer oil change intervals are due to:

Improved "robustness" of today's oils, with their ability to protect en gines from wear and heat and still deliver good fuel economy with low emiss ions More automakers using synthetic oil Tighter tolerances (the gap between metal moving parts) of modern engin es The introduction of oil life monitoring systems, which notify the drive r when an oil change is required and are based on the way the car is driven and the conditions it encounters. Sixteen of 34 carmakers now use oil life monitoring systems in their 2013 model-year vehicles, including all three domestic automakers. That represents a majority of the vehicles sold in the U.S.

One GM car Edmunds drove went 13,000 miles before the monitoring system ind icated the need for an oil change. We sent a sample of that oil to a lab fo r analysis. The results showed that the oil could have safely delivered at least another 2,000 miles of service.

In fact I had read that very report before posting here. But does that mean that I can run *my* vehicles for 10,000 miles between oil changes? I'm not so sure about that. Neither of them has continuous monitoring systems.

And even we stick to the specified 3000/5000-mile oil change intervals, what about the "or three months, whichever comes first"? Is the time between changes still important with modern lubricants?

Perce

Indeed. Doesn't need to be a lot, though.

This is likely true.

--scott

The only way to tell for sure is to send your oil out to a lab for analysis. (Send it out after 3000 miles, have it checked, and you can make an informed decision as to whether it's safe to go for longer intervals.)

If you do go for extended oil changes you should also use a filter designed for longer service, or change it as needed.

ct engines from wear and heat and still deliver good fuel economy with low emissions

driver when an oil change is required and are based on the way the car is d riven and the conditions it encounters. Sixteen of 34 carmakers now use oil life monitoring systems in their 2013 model-year vehicles, including all t hree domestic automakers. That represents a majority of the vehicles sold i n the U.S.

indicated the need for an oil change. We sent a sample of that oil to a la b for analysis. The results showed that the oil could have safely delivered at least another 2,000 miles of service.

Sample was sent to lab which includes far more testing than continuous moni toring systems.

If you want to waste money changing every 3K, it's your money.

Andy

To

Andrew Kennedy

Message body

They will shear, but that's one of the main benefits of using a synthetic b ase. It has a higher natural VI so that not as much VII is needed to get th e desired results. Not as much in there = less likelihood of shearing.

Thanks,

Jeremy Wright

I use a filter designed for full synthetics.

Andy

Every 3,000 if you're using dinosaur goop. Every 6,000 for synthetic. That's just what I recommend.

My 2013 Subaru Forester requires synthetic only, per manual, and states 3 months/ 3750 miles oil change interval. So despite synthetic oil engineers at Subaru still want you to change at 3 mos.

This is intriguing!

It is a turbo car, but other non-turbo Subarus also have the same requirement for severe service-

I like what Scott Dorsey says in his first post. Interesting thread, btw.

Regarding oil analysis testing, for example the popular Blackstone Labs service, it gives you only recommendations based on universal averages- which means averages from a database, a universe, of previously sampled oils. If you understand what that truly means you will know that testing is not an a foolproof anwser. You may be told to extend your drain interval because your wear numbers are low, ...whereby "low" mean that they are lower than the universal averages as sampled by previos customers with similar car models. Tells you only that you are doing better than others with similar cars, not whether this is the best OCI (oil change interval) for engine wear prevention from a technical perspective.

I like to change synthetic at 3000 miles, or even less if the car has been driven hard. I kind of ignore the 3 mos. requirement, but always change oil before and after winter.

Basia

Right. You can't just take one sample and know anything useful about your engine, you need to keep continuous systematic testing so that you can effectively plot trends.

It tells you nothing of any real use to have a single sample. If you are running a big marine engine or an aircraft engine, systematic oil testing is worthwhile, both a cost savings and an accurate failure predictor. If you're running a car engine it's a pretty silly idea.

I tend to change at 3,000 miles, but I can't tell you that this is worthwhile or not worthwhile. And nobody can tell you unless you're prepared to spend a lot of money on testing.

--scott

Engine oil test kits. What about those?

Our shop tried many oil change intervals for hundreds of vehicles driving in "normal use" in the heat of AZ. They decided 7500 miles/6 months was the sweet spot. When I use synthetic I figure anywhere from 1 to 3 years is good depending on the miles which may range from

It is one of those things that just never gets settled.

My owner's manual says 5000 miles for oil changes, less only if on the "severe duty" schedule (which is not how I drive it). So I pretty much stick to that. I'll go over a bit if I just can't get to it until the weekend, for example.

For the last change, I used a synthetic blend high-mileage oil (i.e. with zinc added for seal and ring conditioning). As the car was pushing 189k miles, I figured it couldn't hurt.

Next change will be a high-mileage full synthetic.

I've had shops tell me 3000 miles no matter what. I think they were just trying to sell oil changes.

Right, because it's so dependent on the vehicle, the condition of the vehicle, and the way it's driven.

And all the actual evidence anybody has is anecdotal.

If you're commuting an hour to work and back on the highway, that counts as severe duty.

Likely, it IS their job to sell oil changes. Then again, oil changes are much less profitable than engine rebuilds.

--scott

I drive ~4K/year, most of it freeway. 98K miles on the 1988 Caddy POS. I change the oil once a year at Pep Boys or Jiffy. It might use half a quart between changes.

:-( 89K, if it makes a difference.

How do you figure that as severe duty??? Those are easy miles unless the whole trip is nothing but 5 mph bumper to bumper. If you are averaging any speed at all and keeping the car fully warmed up it's easy miles.

It's one of the examples of "severe duty" that Ford used to give. I think basically any sort of normal regular driving falls under their definition of "severe duty" and therefore just about everyone needs to be using the severe duty schedule.

--scott