When and how have you personally deviated from the car owners manual

If you count not going by the MM in my wife's Honda I have about 10% oil life remaining. Probably close to 5k maybe 6k on the oil and it was changed in March. Running Amsoil SS so plan on changing next march which might put 7500 to 10k on the oil. Car is split between 2 - 3 days a week highway and 2 - 3 days a week local. I figure by March I will be closer to -15% life remaining. Since the car has 115k miles on it I don't feel so bad.
 
Replaced 5W-30 with 0W-40 in most applications. Not all though ... it depends on the 5W-30 deals I find.

I'm still partial to Kirkland because of its everyday price and Valvoline Advanced for its additives -- when I can find it on-sale.

0W-40 runs oh-so smooth in my cheap GM engines. Butter smooth...
 
My 05 honda crv's manual states to change the oil filter every other change.

I've been changing it every oil change 8000kms with a frame ultra.
 
'15 Sentra specs 0w20. Apparently 5w30 is acceptable by the owner's manual - I tried 5w20 once, and I could tell immediately after the oil change that it was very sluggish on acceleration.

I'm sticking to 0w20 unless it starts burning oil, then maybe I'll try 0w30. Or 0w16 just to get better MPG since the Sentra sucks at city fuel economy too (have to rev the piss out of it to get going from a stop)
 
In our Hyundai and Kia's I just stick with manual. Once out of warranty, I may extend OCI with info from oil analysis. IF the oil still looks good, I extend to up to a year. Our cars get less than 10K a year though (last couple years anyway.) For work I have a fleet vehicle (Ford Fusion.) That gets driven a lot.
 
I use a heavier viscosity oil, change fluids more often than the manual suggests, do more "preventive" maintenance, deviate from the stipulated tire pressure.
 
I have a 2019 Jeep Geand Cherokee with a V6 and it calls for 0-20 and a 2021 GMC Canyon V6 that calls for 5-30 both require synthetic. After warranty I will use 10-30 synthetic in both. Don't want any reason for a denied engine claim although oil related failures seem to be rare these days.
 
I have 2006 Holden (Opel) Astra and the owners manual says to use 10W30 or 15W40 in ACEA A3/B3 or A3/B4. That's it. No other viscosity is listed, and no other standards like API are listed.

First oil I ran was Valvoline DuraBlend 10W40 A3/B4 semi-synthetic, close enough. Followed by other name brand A3/B4 10W40s as they are cheap and plentiful here.

I also ran some full synthetic A3/B4 oils such as Castrol Magnatec 5W30, Shell Helix Ultra 5W40, and Valvoline SynPower 0W40. Still no great risk, as they still carried the correct Euro spec, even if a slightly different viscosity grade, mostly the winter rating - which is nothing in my hot climate.

Probably my biggest deviation was Mobil 1 5W30, which was a ILSAC GF-5 and Dexos1 oil, so completely off grade and off spec. But hey, years down the road, and I'm still driving the car.
'99 Ford F-150. I never changed the transmission fluid. It got to the point where the truck had 150K on it, I bought it with 60K on it and had never changed the fluid. At that point, it was running fine and I feared that flushing the fluid would cause problem.
Kind of the same thing with the radiator fluid too. I ran it 130K before I flushed the radiator and when it came out, the fluid looked like black coffee. Not good.
I cant say that I was always good to that truck but it still make it 214K before I traded it in.
 
I just did an oil change on my 2006 GM Astra, car in the opening post. Big oil deviation from the OM this time by going to an old school monograde. Except it's probably much better than the old Group I stuff used years ago, now that we can get Group II monogrades with significantly lower pour points (PP), higher viscosity index (VI) and much better oxidation stability.

I used a Penrite SAE 30 Monograde that is API SG/CD, non-friction modified, with VI = 113 (Group II) , Zinc = 1170ppm, TBN = 6.5, SA = 0.67%. Colour = red.

Looking at similar oils I’m expecting the HTHS ~ 3.3 to 3.4 cP and Noack ~ 5% and PP around -30C / -22F.

The TBN is a bit lower, so I'll probably change a bit earlier at 8,000km / 5,000 miles, while keeping the Valvoline syn-blend media filter in for a second run.
 
11 Mazda6 - manual specifies 0w20. Started using 5w30 at 150k miles because old time mechanic recommended it for high mileage to help with top end noise.
 
My 08 Liberty says to only use 5W20 oil. I have ESP 0W30 in it, and will continue to use either 0W30 or 5W30 oil. I'm using ESP 0W30 in a 2016 Jeep Wrangler as well.
 
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