My question to begin this thread was in the form of a hypothetical. Most responders assumed I was talking about my own vehicle since I described it. Fair enough but it was an assumption since I stated that the question applies to any vehicle. Leasing the vehicle has nothing to do with it. The confusion is partly my fault because we got off track in discussing warranty coverage requirements.
To be honest, I had forgotten all about the time interval requirement in the owner’s manual for scheduled maintenance. After 17 years of “ownership” (minus 3 years of leasing), I treat the 5,000 mileage requirement as the rule for having these services performed at the dealership and, it turns out, have done so since the first one when I was leasing. That first scheduled maintenance took place at 5,112 miles and 8 months. No objection about being two months late from the dealership (the lessor). The next three scheduled maintenances, including the oil changes, took place at 9.5, 5, and 10 months. After that I purchased the car but continued the practice of following the mileage requirement to determine when to have the maintenance done. Over the 17 years I have owned this SUV, the average time span between servicing has been 8.8 months, well past the 4 or 6 month interval stated in the manual. Since 2015, my wife and I have driven less because of health problems and the intervals between maintenance servicing have been 10, 12, 14, and 12.5 months.
In short, since the beginning, I have disregarded the manual’s time interval guidance and followed the mileage guidance exclusively, although I chose the 5,000 mile standard instead of the 7,500 mile rule which I could have followed based on the type of driving to which this vehicle is subjected.
I have already mentioned that no Lexus mechanic (I have the vehicle serviced only by Lexus dealerships) or service manager has ever expressed concern about exceeding the time intervals between servicing. I have also mentioned that some automotive websites also mention only the mileage requirements for oil changes to avoid engine damage although others, including the Consumer Reports link in this thread, do include the time interval guidance.
So here’s where I end up. Many of you will not agree with my conclusion. No need to rush to tell me so. No need to send me pious “tsk tsks” either or remind me that it is my vehicle and my pocket book.
I don’t think manufacturers who include both a mileage and a time interval guideline for scheduled maintenance are serious about the time interval. It actually doesn’t make sense. It would make sense if it applied only to oil and filter changes but it doesn’t. There is no separate schedule for oil changes. They are included in a list of scheduled maintenance services, many of which address the condition of parts of the vehicle that deteriorate almost exclusively from use; i.e., from being driven. Based on the manufacturer’s assumed driving mileage (1,250 miles/month in my case), some of the planned maintenance services are considerably more extensive (and expensive) than others. This is because at those points in a vehicle’s usage, there is wear and tear expected that may call for repairs. Applying a time interval to this scheme for drivers who are well below the 15,000 miles per year driving level, as I have been, ends up scheduling extensive maintenance services long before they are needed based on projected usage levels. That is not only an unneeded and probably useless extra expense, it also can have the opposite effect of producing a limited maintenance service at a time when a more extensive one should have taken place since servicing is no longer tied to actual usage. The only element of the servicing that makes sense for this is the oil change, which is on the list for maintenance at every service. But if the manufacturers were really concerned about getting the oil changed more frequently for inactive drivers they would create a separate maintenance schedule for it. Of course, then owners would be bringing their vehicles in for at least some servicing (oil and filter change) multiple times a year. Not that appealing for marketing and competitive purposes. And suggesting the owner visit his local “Jiffy Oil Change” is not something any dealership will be keen on for a number of reasons which you can figure out yourselves.
Some may respond (oh, have already, in fact) that failing to get the oil changed according to the specified time interval jeopardizes warranty coverage. I’m a lawyer and I’m going to tell you why that’s not legally correct even if a dealer uses it to deny your coverage in case of a defective engine not caused by tardy oil changes. But, first, my conclusion is that an annual oil change tied to normal vehicle usage of 5,000 miles per year exclusively on city streets and highways will not produce damaging engine sludge nor cause any other vehicle damage. [This is an opinion, old-timer_11, but it is also based on 17 years of experience.] How much longer could I safely go? That was my original question but no one actually tried to answer it. I did get some good guidance and insights, though, and I intend to follow up with the Blackstone Labs test just to confirm my conclusion. If it turns out I’m wrong, I’ll come back here and report the results, assuming I can find this thread again.
Free legal advice: If you have a valid warranty claim, do not be put off by the dealer’s assertion that you failed to follow some maintenance requirement and, therefore, have voided your warranty and lost your legal protection. This is true only if the maintenance requirement you failed to follow actually caused the vehicle damage for which you are seeking warranty coverage. Most states have lemon laws that apply to motor vehicles and most courts are not sympathetic to attempts to evade responsibility by finding some technical but irrelevant violation of the maintenance requirements. Of course, if your delayed oil change actually causes the engine damage, bye bye warranty coverage. My conclusion, however, based on my decades of experience with multiple vehicles, is that an annual oil change will suffice if usage requirements are maintained.
Please note, also, that I am not representing anyone on this thread and my legal opinions are not intended to be the basis for any decisions you may make. You need to consult your own attorney for that.
Thanks, all. It’s been a really good learning experience for me and, despite some bumps in the road, I ended up with a good answer to my question. No need to tell me you disagree.