I'm confused because you state mechanics don't know anything, but forum posters don't know anything...well...somebody has to know something 😆

 

There's little data available. Manufacturers have warranty claim data but they're not sharing it; repair data after the warranty period is scattered among dealerships, chains, independent shops and shadetree mechanics. It's relevent that the push for more frequent fluid changes comes primarly from those who profit from it, supported by scary anecdotes and folksy truisms ("fluids are cheaper than metal"), but no data, much like the current scam of car and home maintenance "warranties." Some people are very receptive to that message; I still know a few people who change their motor oil every 3000 miles because Pennzoil and Valvoline ran TV ads years ago telling them it was critical. Consumers Union ran a large-scale tests on a taxi fleet to test that claim and found no difference in engine wear between 3000 mile changes and the manufacturer's recommendation. Tests have found modern vehicle oil life monitors consistently conservative, so I tend to think the manufacturers know what they're doing.

As someone with a few decades of personal automotive, fleet and stationary machinery maintenance experience, my experience is that premature failures usually result from defects or some sort of abuse (including other maintenance failures), and changing fluids more often than recommended won't change that. It's very important to use the right spec, and change it in accordance with manufacturer recommendations for the particular machine and operating conditions. I don't know if changing fluid twice or three times as often will be the difference in a transmission lasting 280K miles instead of 260K, and probably nobody else can claim to know either, but at that point a vehicle isn't worth the extra maintenance cost over its lifetime for such little gain, and I'm probably not going to be the one driving it then anyway.

 

I had Ford Pass points to spend, so I had the trans, brake, and diff/transfer case fluids done at 40k miles. Just for peace of mind, really.

Each engine has their own issues. The 3.5 EBs are known for cam phaser issues. The 5.0s have IMRC issues. Lots of other possible premature failures, but they’re the exception, not the norm. You come on these forums and usually only hear the horror stories. Just regular maintenance is key, IMO. It’s like googling medical symptoms…you will eventually be thinking you have cancer. 😂😂

 

I am of the opinion/experience (just shy of 50 years driving now) that prudent fluid changes are a really good idea for long term reliability if you intend to keep a vehicle for the long haul - meaning many years, many miles, or both. The vast majority of us drive under the OEM severe service classification. OEM calls for transmission fluid change at 150k; you are at 125k and anticipating/debating whether to keep the truck for the next 150k. It's time to change it.

Most people don't keep their vehicles long enough for prudent maintenance procedures to make a difference. I do my own maintenance, so I save a ton of money over the life of a vehicle. I'll do my good quality full synthetic oil and filter changes at 5k miles for peace of mind that I won't have early cam phaser issues or a stretched timing chain on a DOHC V6. Brake fluid change every 5 years maximum. Coolant change every 5-8 years, depending on mileage driven.

We all make our maintenance choices and live with the consequences. I don't want to have to worry about a breakdown on a 15 year old vehicle when I start on a 3000 mile vacation trip, so I choose shorter maintenance intervals.

 

That CR testing was done on the 3800 OHV V6 engine. Way different than today's OHC, higher stressed engines. Of course, engine oil has also gotten much better over those years.

There were noted early failure issues for the 3.5 ecoboost for people who stuck with the OLM change intervals - cam phasers and stretched timing chains. GM also had failures on their PV6 (3.6L V6) DOHC engine - stretched timing chains - for people who stuck to the OLM change interval. They actually issued a recall to reprogram the OLM system from a 10k-12k mile change interval to 6k; we owned a 2008 Buick Enclave. We only owned it for 8.5 years and 90k miles, so we never had an issue with my 5k mile oil change intervals.

As I indicated in my post just prior to this one, we all pick our maintenance poison (preferences) and live with whatever happens because of those choices.

 

I don’t drive my truck much these days, working from home, but the environment I drive in is considered “severe service”. The owners manual recommends much shorter service intervals for severe service operation.

 

Typically about half of the "normal" service interval.

 

We do, and if you're the type that's going to drive a truck until the wheels fall off, or for certain uses like lots of towing, idling, or off road use, early fluid changes aren't a bad idea. They don't hurt anything.

However, as we've already proven here, most of us do not drive under Ford's definition of severe service (don't make me find that survey again). For those who do - the engine oil life monitor detects and takes those conditions into account.

 

We will just have to agree to disagree regarding severe service. Short trips, towing, stop and go city driving all come under the heading of severe service. As does driving in high heat and severe cold conditions.

 

Ford has specific definitions for "Special Operating Conditions," all contained in the Scheduled Maintenance section of our manuals. Worth a look. When I ran a poll some time back, using Ford's definitions as the selections, about 10% of those who responded fell into Special Operating Conditions by their own estimation. It's another motor oil company falacy that "most" drivers put their vehicles through severe use (cited in ads pushing early oil changes). Agree or not, the manufacturer defines severe service for their product. Ford's only recommendation for engine oil changes under all conditions other than dust, is to go by the oil life monitor.