Trying to establish a rational oil change interval

Discussion in 'Clarity' started by Fast Eddie B, Aug 27, 2019.

  1. Our 2018 Clarity is ready to turn over 20,000 miles. The first oil change was around 10,000 miles, and was free at the dealer. I have already bought the requisite oil and filter to do the next one myself.

    But when? Oil changes every 10,000 miles has worked fine on our 2005 Element over about 20 such changes. 10,000 miles is a nice round number, and fresh oil and filter makes for cheap insurance.

    But it also seems wasteful. I figure that only 30% to 40% of our miles are with the engine running. So, changing oil at 10,000 miles means the engine has only been in use for 3,000 or 4,000 miles. Given modern synthetic oil and the fairly light loading of our little Atkinson Cycle engines, it would seem to make oil changes this frequent totally unnecessary both from a financial and ecological perspective.

    Leaving possible warranty issues out of the picture, how many here might defend letting the oil run 15,000 or even 20,000 miles, keeping in mind that even 20,000 miles would equate to about 8,000 miles of the engine running in our use case.

  2. markc

    markc New Member

    I would pay more attention to time than distance since we really don't have a way of knowing how far we travel using the gas engine. With synthetic oil you really don't see any recommendations that are longer than 1 year for the oil change and many are 6 months. I hardly drive my truck at all the days but I do get the oil changed twice a year none the less.
  3. MPower

    MPower Well-Known Member

    For what it's worth, my 2012 Prius Plugin did not have any fancy maintenance minder. The owners manual gave the recommended service intervals based on mileage. It used synthetic oil and the oil change interval was 10,000 miles. Bear in mind that the EV mileage on the GOM was rarely more 10 miles so the ICE ran much more frequently than it does on the Clarity.
  4. graure

    graure Member

    If you do less than 10K ICE miles per year, I think just do an annual oil change in the summer when it's nice out. No sense in exceeding the oil manufacturer's guidelines for service life though.
  5. fotomoto

    fotomoto Active Member

    Ours gets driven in HV each workday for at least 30 minutes highway so the oil is getting both used and to proper temps so I'm comfortable with going with 10k intervals on mobil 1 syn 0w20. OTOH, my Energi OCI recommendation is 2yrs/20k miles but I change it at 2 yrs since it is mainly used in EV and only racks up about 3-4k miles/yr.
  6. Sandroad

    Sandroad Well-Known Member

    Wow, 20K miles already. You and Karen boogie. :cool: IMHO (worth what it cost you), the Clarity is fine with an annual oil change. Very few (none, really) of us will ever get to enough ICE miles in a year to stress modern synthetic oil. Pick a convenient time and put in the good stuff. That also matches the owner's manual that states annual change as the maximum interval.
  7. Agzand

    Agzand Active Member

    It really depends on your driving situation. If you are doing road trips in high altitude, the engine will run at high RPM for extended periods. So I think it makes sense to change it after 2k-3k miles of ICE use under these conditions. For regular commute at lower elevations I think 10k-15k miles overall with 3k-6k ICE miles should be OK. I believe when the engine runs at a bit higher RPM than similar ICE cars, so I definitely don't want 10k miles of ICE use on the same oil.
  8. KentuckyKen

    KentuckyKen Well-Known Member

    Boy, you’ve really opened up a can of worms on this topic. I predict responses will be all over the place.
    At the insistence of my lawyers I must start by mentioning that the manual states to change the oil at least once a year.

    My limited understanding of tribology tells me that oil wears out or no longer gives adequate protection due mostly to 4 factors:
    -Moisture build up
    -Loss of protective additives
    -Inevitable loss of lubricity due to oxidation and breakdown of the long chain oil molecules
    -(some add sludge formation, but that’s really caused by the above)

    Obviously, lots of us won’t get enough HV miles or engine run miles to significantly effect the above if we just go by total miles like the MM seems to do. So I think the real question is how long can oil sit in an engine that is not run much before it becomes a problem.
    That seems to be very subjective and I think can only be quantified by paying for an oil analysis.

    I’ve made the decision to change my oil once a year even though I only drive 750 miles, out of 8,000 total, in HV plus the occasional short System Check runs.
    As previously mentioned, it’s cheap insurance at once a year since I really don’t know exactly how time alone affects the oil as in how much or how damaging is the oxidation, acidification, and moisture build up in a slightly run engine. YMMV.

    If you really want to pursue this issue in exhausting detail, just go to But be warned that there are several life times worth of rabbit holes to go down on that site. But it is the best source of info that I’ve found.
    ClarityDoc and bpratt like this.
  9. Sandroad

    Sandroad Well-Known Member

    Interesting observation. Having nothing else to do while I watch a puppy sleep, I’ll speculate on why I disagree with higher rpm = more frequent changes. I think it’s really the load on the engine that counts, not the rpm. I think an engine “lugging” (straining) while running at a slow rpm under heavy load is potentially wearing internally more than an engine allowed to spin freely and “breathe” a bit under the same load. Load in this case is HP needed, where HP is roughly torque times rpm. Further, I think this is especially the case with Honda engines that spin up so happily. In addition to the load aspect, it seems to me the engine-generator setup is ideal for optimizing oil life. The engine tends to run at a constant rpm more often than an ICE-only vehicle and that optimizes mpg (for this drivetrain) and minimizes contaminates like gas and combustion products that ultimately reduce synthetic oil life. Synthetic oil does not break down like dino oil and really only needs to be changed because of contamination from engine operation ( I read that on the Internet so it must be true). An engine sitting and running at a constant rpm (even a high one) for an extended period may have few contaminants in the oil than an engine going up and down in rpm over and over for the same period of time. One caveat is that cold engines tends to wear more and potentially contaminate the oil sooner and that may be the case with the Clarity which starts and runs the ICE for short bursts occasionally. But, that issue has nothing to do with high rpm = more frequent oil changes. Bottom line: IMHO, the Clarity drivetrain optimizes oil life and “let ‘er breathe” without worrying about rpm.
    insightman and 2002 like this.
  10. Agzand

    Agzand Active Member

    Well, I am not sure, but a couple of Honda generators that I checked have oil change interval of 100 hours or 6 months. The fact that engine is used sparingly often is not necessarily a benefit to oil, it could result in moisture contamination and early degradation.

    On of the operation modes of Clarity (the gear mode or engine drive mode) could also considered lugging the engine. I noticed that the car uses this mode even in some uphill sections.

    Oil degradation is highly correlated with temperature. Higher RPMs could lead to higher temperatures, although it shouldn't be as bad a a turbo. The mechanical shearing of the oil due to high RPM could also degrade the oil. A turbo definitely is much harder on oil, but relatively small volume of oil goes through the turbo.
  11. 2002

    2002 Well-Known Member

    For most drivers that's probably not very often. Once in HV mode the engine stays warm as it only turns off for very brief periods, similar to a regular hybrid. Cold starts while in EV mode due to hard acceleration are more rare. Any extra wear should be more than offset by the complete lack of engine startup on many EV only drives.
  12. craze1cars

    craze1cars Well-Known Member

    Once a year. Your usage is similar to mine. We have cleared 20k on our Clarity in 11 months of ownership. I’ll speculate our ICE usage is closer to 50%. I will be changing annually, and rotating tires every 7500ish.

    My ICE vehicles get the same annual treatment. 12k to 15k on each is typical. Sometimes more rarely less. 2007 Mazda has nearly 200k and running strong as new. Silverado is newer but most of those miles on the truck are towing boat and snowmobile trailers on the interstate. I can’t recall the last time any of my vehicles have darkened the door of a dealership save a recall campaign. I do all maintenance and repairs myself.

    I do use full synthetic.

    FWIW, Mobil 1 recommends 15k oil change intervals, Amsoil 25k interval. And those are for ICE cars.

    Oil changes are the most frequently agonized and overdone maintenance concern among car owners. With annual synthetic oil and filter changes these engines will last the useful life of the car.
    Last edited: Aug 27, 2019
  13. ryd994

    ryd994 Active Member

    The only rational is to keep the warranty at the moment......
    After the warranty expire, I'd say annual change with good synthetic oil should be more than enough
  14. Just curious... it even possible to buy 0-20W that’s NOT full synthetic? I was price shopping at WalMart and didn’t see any.
  15. craze1cars

    craze1cars Well-Known Member

    I dunno. Doesn’t really matter...
  16. Thanks for all the input.

    Right now my plan is to look for the date of my first oil change and plan a change a year from then. Or maybe a tad earlier if we plan a long cross country.

    As an aside, I concur with Sandroad that higher rpm does not necessarily correlate with increased wear. In a properly functioning engine, there is virtually no metal-to-metal contact - parts are separated by a thin film of oil as long as there’s oil pressure. If they weren’t, the engine would grind to a halt in very short order.

    As a further aside, I like to use quality oil, but think any major brand is fine. I had to look in the garage to see what I got, but this time ended up with Castrol GTX Magnatek*. Lubrication-related failures are vanishingly rare in modern engines if properly maintained. I personally think “specialty oils” like Royal Purple or Amsoil are a waste of money.

    *Its got “Intelligent Molecules”! How can I go wrong?!?
    Last edited: Aug 27, 2019
    MPower likes this.
  17. craze1cars

    craze1cars Well-Known Member

    Agree on all counts. Oil brand is irrelevant, and as far as “high rpms”...Clarity engine simply doesn’t run high rpms. It redlines at only 5500, which is pretty low, and according to everyone posting their rpms here on his site it essentially never reaches that number anyway. It’s just incredibly noisy and unrefined, so people think it’s spinning faster than it does.

    Heck my old stickshift Mazda 3 has a 7,000 rpm rev limiter and maintains about 3500 rpm at 75 mph in its top gear, and while doing so it doesn’t sound like it’s working...unlike the Clarity which definitely does sound like it is under duress. But it really isn’t.

    Clarity’s 4 banger is a high quality, albeit low performance, engine that doesn’t stress its oil hardly at all by modern standards.
    Last edited: Aug 27, 2019
  18. css28

    css28 Active Member

    Actually, GM allows up to 2 years on the Volt's oil change if the engine use is low enough.
  19. 60Hertz

    60Hertz New Member

    Since the answer depends on how much the ICE runs, which will vary greatly between different owners, the best measure is how much fuel has been burned. In HV mode, ballpark figure about 40mpg. For example, if you've put in 100 gals of fuel, then the ICE has run for about 4000 miles. To keep track, I have a notepad in the console to write down fuel when I fill it. As others have said, I would change once per year at a minimum.
    Fred Davies and MrFixit like this.
  20. KentuckyKen

    KentuckyKen Well-Known Member

    All 0-20W oil is full synthetic or partial synthetic (the rules for synthetic oil have been dummied down). There is no 0-20W dino oil made.

    And FWIW, Amsoil is definitely different from other brands and can be argued as to whether it’s better. The real question is not is it different/better but is it worth the price differential for what you get. Since I only change oil once a year, $10 or $15 more is not that big a deal. But truth be told, any API certified oil changed as needed is going to do just fine.

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