Minok

In the world of magic purple unicorn oil variants this would cause even more calls if heresy.

But it why even bother changing ( that is draining and replacing) the engine oil? Why not just replace filter once a year and top off with fresh oil as needed?

there was a German tv show on a major network there that posed the question.

https://youtu.be/3G1nmhSZvN0

some cars driving for hundred thousand miles without n oil change. The suggestion is it's the garage and dealer relationships maintenance and the big profit margin on modern synthetic oils that keeps us all addicted to the tap.

SoCal C2S

Go for it....for $100/year for oil this seems like something equal to "can I put 87 octane in the tank instead of 91?"

KNS

The oil itself will maintain its properties for a very long time. It will accumulate dirt (even with religious filter changes) and the byproducts of combustion and that is the real reason you want to change it out.

It's you car, do what you want. Just let the prospective next owner know you never changed the oil, I'm sure he'll want to know.

Mike Murphy

It's because the filter is not the same kind of filter that's in your house HVAC. Your house HVAC or HEPA vacuum cleaner actually can remove dirt, but an oil filter mostly can only screen debris.

Changing the oil is really the only way to get the dirt and contaminants out of the engine.

cool flash

The oil stock base will last for a long time.

The additive package in the oil (anti-corrosion, anti-wear etc.) will degrade over much shorter time and become ineffective.

If you wanted to keep using the old oil you would not only have to filter out the contaminants but also replenish the additives. Not really practical in real life...

Just change your oil and filter every 12 months and you are golden.

CF

Ben Z

Any oil analysis data from credible sources to back that up? If not then I think I'll keep changing my oil regularly.

mcfisticuffs

If I had a 30 year old Golf that burned oil, totally would do this.

However... I don't...

I give the dealer their $$ for the annual official pre-winter-storage oil change, and do my own part way through the driving season. It's a few $00...

Now, if you find a way to not have to replace the rear tyres, I'm listening...

Mumbles

At the end of the day its a lubricated engine. Expensive to replace or repair so why bother eliminating basic maintenance procedures ?

It may be the next guy who gets your car may get to do the repairs...

Racetwin2

Because you have a 50K + car and oil cost nothing.

But I would agree somewhat. Filter is almost more important than oil. However debris/particles in oil increase exponentially so if you start with almost zero (new oil) it will take a very long time until particles increase. But if you already start with some particles it will increase/escalate much faster.

Secondly - oil gets diluted with water and gasoline so that is another reason to change also the oil.

Draining for a long time is good in order to remove as many particles in the oil as possible. That is why some people let it drain for hours.

Mike Murphy

The math is still important, though, when folks spend too much on oil changes or change too frequently.

Example: A guy that worked for my Dad had 350,000 miles on his 1985 Chevy Truck. He changed his oil every 2500 miles and was proud of it. The cost? 140 changes at $35/change = $4900 (roughly the cost of 2 engine rebuilds at the time).

Advise: $15/quart oil is not twice as good or lasts twice as long as $7.50/quart oil.

Petza914

KNS & Cool Flash have provided the correct answers to this question. The filter can't catch all of the combustion byproducts and the additive package breaks down over time. If you've ever had a UOA done on the same brand, type, and weight of oil used under the same conditions, but at different mileage intervals, this becomes evident in the Flashpoint values at the different temperatures and in the TAN & TBN values. Essentially, one the additive package starts breaking down, you're 5W/40 starts behaving like 5W/30, then 0W/30 and the degradation continues from there.

One of the primary advantages to synthetic base stock oils over petroleum ones is that all the molecule sizes are the same so the oil is more homogenous and more consistent rather than an average of natural molecule sizes. For example a synthetic base oil with a weight of 5 has all molecules of size 5, wheras a natural petroleum derived oil has molecules of varying size that average to a 5, some larger and some smaller because they're natural (like no 2 snowflakes are identical).

So although a synthetic base stock oil (M1, Motul, DT40 etc) is more uniform and stable over a longer period, it still gets contaminated and the anti-wear additive package added to the base stock still breaks down and gets used up over time.

Iceter

Five quarts of Pennzoil and an AC Delco filter cost a lot less than $35. If he was changing his oil himself, he was paying maybe $8 for he supplies. Even if he was paying Quik-Lube to do it, he was paying less than $20 per change.

Iceter

I have a buddy with a '68 Mustang his dad bought new. The car has over a quarter million miles on it and both he and his dad changed the oil every 2,500 miles. The car runs great. The car is definitely worth more with the original engine than it would be with a replacement. Probably worth more than they spent on all those oil changes at $8 per.

But I freely admit that 2,500 mile oil changes is serious overkill, not to mention a huge PITA and environmentally unfriendly.

Mike Murphy

Come to think of it, my math was wrong. I used the cost of the engine rebuilds as-if he paid someone to do it. He always changed the oil himself and knew how to rebuild engines.

So if the cost of oil and filters from 1985-1997 was really around $8 average, then I have to assume that an engine rebuild - machining the bores, new rings, new bearing, maybe a valve job - would have cost closer to $800-$1000 if he did the work himself - then we are comparing $1,140 in oil changes vs. less than that for an engine rebuild.

My only point is that economics are involved in reasons why cars don't come with a fancy oil regeneration system, and folks who buy really expensive oil should consider those costs versus the alternatives. Racing oil aside, folks who believed that replacing street oil every 3,000 miles (common in the 1980s and 1990s) could have actually spent more money on oil changes than the cost of an engine rebuild. These are the reasons why I believe most folks have graduated toward 5,000-miles changes.

However, I'd still like to make the point that even folks doing changes every 5,000 miles should consider going with cheaper oil (there are a few Class 5 oils that are 1/2 the cost of other Class 5 oils) on the basis that they aren't 1/2 as good, but rather 85-90% as good. The difference in cost could help pay for future engine work that might be needed regardless.

Then there are those that stretch to 7,500+ miles or more. Suppose a taxi driver is driving around on 15,000-mile oil. Doing so in a Porsche is not economically smart, but doing so in a 1990's Crown Vic, provided an engine rebuild is cheap, might be better off with extended oil intervals using a Class 5 oil priced in the $6-$7/qt range.

In the extreme cases, I believe folks are still changing filters and then oil every year still.

Petza914

...except this is a Porsche forum, where rebuilt engines aren't a couple thousand dollars, they're $20,000 or so and that's a heck of a lot of even boutique oil. Also, what about the value of not having access to drive the car while the rebuild is going on - rental car companies call this "Loss of Use" and if you have an accident in one of their cars, bill you (or your insurance company) for the days it's not available for rent in their fleet so that cost should also be factored into the analysis.

I don't see how anyone can come out ahead by not changing oil and filters to the point where it results in engine failure, and that failure likely won't occur in your garage where it's convenient. I'll happily continue along with my $150 DT40 oil changes every 4-5,000 miles to avoid premature engine failure in one of my P-cars, but to each their own.