Oil
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Intermediate
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From: CA
Oil
I know this is discussed and specs for the model are clear. BUT, I put less than 1000 miles on my RCF every year. I change oil annually. I'd like opinions whether you think, given how much I drive, it matters whether non synthetic, synthetic blend or full synthetic makes any difference at all. My driving is around town mostly with occasional freeway.
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I am in the same shoes as you. I take it to the dealership once a year and have it fully inspected with scheduled maintenance and have the oil changed even if it is parked 90% of the time.
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From: wa
The common practice of used oil analysis has given us an enormous data set on oil life. And it turns out it’s use and miles/combustion by products that cause degradation, not time (which is what we’ve known all along anyway).
Time change interval thoroughly debunked, note and linked here:
https://www.reddit.com/r/cars/commen...nterval_myth/#
From Blackstone data set examples:
Time change interval thoroughly debunked, note and linked here:
https://www.reddit.com/r/cars/commen...nterval_myth/#
From Blackstone data set examples:
First test was 2020 Ford F150 for oil in the car for 6 months, for the drivers who worry about 6 month longevity. The oil was still good for another 2,000 miles.
Second test. 2017 Wrangler. 2 year old oil, 5000 miles. Oil was still good.
Third test. 2000 F350. 2 year old oil. Oil was still good.
Fourth test. 1997 Towncar. 5 year inactivity oil. Unkown miles. Oil showed normal wear but no unusual breakdown that would suggest time based reasons.
Fifth test. 1984 F250. 6 year inactivity oil. Same wear of steel parts in the oil, but again, normal physical properties of the oil itself.
Last test. Mobile 1 10W40 in a 1995 Porsche 993. 10 years old, 760 miles. Oil was in perfect condition.
To summarize, time alone is NO reason that full synthetic oil would be unusable. Of course there are many other factors. He says it's a misconception that oil breaks down over time. Miles are what you have to keep track on.
Second test. 2017 Wrangler. 2 year old oil, 5000 miles. Oil was still good.
Third test. 2000 F350. 2 year old oil. Oil was still good.
Fourth test. 1997 Towncar. 5 year inactivity oil. Unkown miles. Oil showed normal wear but no unusual breakdown that would suggest time based reasons.
Fifth test. 1984 F250. 6 year inactivity oil. Same wear of steel parts in the oil, but again, normal physical properties of the oil itself.
Last test. Mobile 1 10W40 in a 1995 Porsche 993. 10 years old, 760 miles. Oil was in perfect condition.
To summarize, time alone is NO reason that full synthetic oil would be unusable. Of course there are many other factors. He says it's a misconception that oil breaks down over time. Miles are what you have to keep track on.
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Sae did some tests. Oil does not degrade in a closed system ... You know this since the bottles of oil on the shelf are still good a decade after bottling. What the other finding was about temperature. Heating oil does degrade it. Heating oil very hot degrades it more. Oil in a non closed system will degrade. The mfg suggestion for time interval changes is in case you do frequent short trips which means frequent heat and cool cycles which, in their mind, is just as bad as many miles of very hot oil.
But that is not what I was asking.
Does it matter in your opinion whether I put regular oil, synthetic blend or full synthetic in. I've been using a blend for the past few oil changes and will likely do it again.
But that is not what I was asking.
Does it matter in your opinion whether I put regular oil, synthetic blend or full synthetic in. I've been using a blend for the past few oil changes and will likely do it again.
^^^^^This is just IMHO
But, to me - The cost of oil is really not a big deal. The cost difference between dino oil, blend, or full synthetic is really not that much. And there are different grades of full synthetic. My Oil maker of choice, Pennzoil, offers three grades of full synthetic. I use Ultra Platinum, the highest of those three grades. Why - Because it's been proven to me that the greatest amount of engine protection will be provided by the oil that flows the best under extreme temperatures and with the most anti-wear additives that aid in keeping the sludge in suspension. That peace of mind is worth the few bucks more a premium full synthetic costs. Less expensive oil, IMHO, is just not worth the small savings versus the big savings you will reap in a healthy engine.
Lou
But, to me - The cost of oil is really not a big deal. The cost difference between dino oil, blend, or full synthetic is really not that much. And there are different grades of full synthetic. My Oil maker of choice, Pennzoil, offers three grades of full synthetic. I use Ultra Platinum, the highest of those three grades. Why - Because it's been proven to me that the greatest amount of engine protection will be provided by the oil that flows the best under extreme temperatures and with the most anti-wear additives that aid in keeping the sludge in suspension. That peace of mind is worth the few bucks more a premium full synthetic costs. Less expensive oil, IMHO, is just not worth the small savings versus the big savings you will reap in a healthy engine.Lou
Last edited by flowrider; Sep 9, 2025 at 08:58 PM.
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why would you want to use a BLEND, that is the question? and on a RCF?? To me, no sense. You do know that a blend is basically just 10-20% synthetic. It's a marketing tag. It's not like you're saving money all that much. Go FULL synthetic and stay w/ your annual oil change interval. Amsoil Signature Series is one such real definition of Fully Synthetic. Pennzoil is another good one.
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From: wa
Sae did some tests. Oil does not degrade in a closed system ... You know this since the bottles of oil on the shelf are still good a decade after bottling. What the other finding was about temperature. Heating oil does degrade it. Heating oil very hot degrades it more. Oil in a non closed system will degrade….
That’s why thermal break-down is not a concern for modern engine oils. The actual laboratory data on this is quite massive and convincing (see Blackstone’s data on it). The SAE has not made an issue out of this since, since around WWII I believe. Oxidative stability renders the time portion of the concern moot - they are quite sophisticated, and effective, at that.
As to your question - if you are going to toss perfectly fine oil every year, just use whatever meets the rec’s. Dyno, semi-syn, syn, they are going to work. If you want to use something BETTER than the recommendations, that’s also on the table.
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From: CA
That is also what I figured. Only reason I change annually is that next owner might be put off by oil changes every 5 years. Just had it done for 2025 at Jiffy Lube. Nice to sit in the car and watch them for 15 minutes.
I change the RC F's and IS F's oil once a year as well, every Spring, before driving them for spring/summer. I use amsoil 5W-30. I put about 1500-2000 miles on each car, but mostly spirited/lots if high revving kind of driving. Some may think it's a waste, but I like amsoil and it really isn't that bad if I'm only changing once a year. I also use the same oil on my daily ('05 IS300) and I change the oil once a year also but it's driven all year round for about 7500 miles/year. I should probably save what I drain from the F's and use it in the daily! 
I drive my RC-F less than 2k miles per year, and I change mine every two years with Mobil1 or Amsoil synthetic.
Oil still looks pretty clean with mostly highway miles. Do you guys recommend changing it annually?
Oil still looks pretty clean with mostly highway miles. Do you guys recommend changing it annually?