I have become more concerned about fuel dilution impacts. It appears one way to minimize these impacts is doing shorter OCIs. I'm trying to zero in on an appropriate interval for my two Mazda's. I was pretty religiously keeping to 5k intervals for both cars. Reading many of the used oil analysis's posted in the used oil analysis section this appears it might now be on the long side. My cars are primarily used for around town driving. Each is taken on a road trip of 500 to 1500 miles about every three to four months or so. About 8 to 10k miles on each per year. I currently use Quaker State Ultimate Protection 0w20 in one car and 0w20 Valvoline Advanced Protection in the other. Besides an OCI adjustment, another option appears to upping the viscosity to 5w30 to address fuel dilution thinning of the oil. Is one of these alternatives better than the other? I'm a geezer (77) and technology is blowing by me. I thought I was being pretty conservative with my current OCI's. The fuel dilution issues have thrown me a curve ball. These maybe the last vehicles I own so I want them to last and need to maintain them the best I can.
How have fuel dilution issues changed oil change intervals
- Thread starter GaryMX5
- Start date
Well, I don't have a Mazda, I have a newer Toyota Rav4. I will post a link to the used oil analysis I had done on it. It had about 2100 miles and exactly 6 months of time on the OCI. It was probably 90% short trip, stop and go to the store driving through the entire Nebraska winter. I had some fuel dilution and a little loss of oil viscocity. I will try to post the virgin analysis of the oil used too, if I can find it. I am going to go 6 months or 3000 miles on mine from now on. I will try to put a couple links here:
Seems like Motul has selection galore when it comes to their engine oils. This particular one is popular amongst Subaru owners. Polaris red flagged it for sodium content. I sent a copy of this to Motul Tech. They said it is their oil, within spec, and the sodium content is part of it. This particular 5-liter jug I bought off of E-bay. It is made in USA, though it is a French company. 
I have not done my own UOA. There are however a number posted here and on other Mazda enthusiast sites that are showing more and more fuel dilution examples/issues linked to 2.5 skyactiv DI equipped engines than desired. I'm hoping there's a reasonable way to address the issue to minimize future impacts.
I would get an analysis done on yours and see how much of an issue, if any, you have and how your wear metals are. Your driving style and weather (winter warm-up, etc) will be different than others.
Just don’t use Blackstone or any lab that estimates fuel through flash point.
How many miles are in these cars? Even with some fuel dilution, at the rate you're putting miles in them, they will still probably be running strong for more than a decade.
The 3 is about 8 months old and has about 6k miles. The cx30 just turned 1 yr old and has about 13K miles. I hope you're right about their longevity!
Increase starting viscosity, change the oil early or both. Best way to mitigate dilution.
I can tell you my data point, my friend's 2016 CX-5 2.5L NA, but direct injection has about 3-4% fuel dilution. If you look up the UOA's I've posted on that you'll see that when they went over 4 months the dilution increased above 5%. I've settled on every 4 months to change the oil regardless of mileage.
I looked into the Mazda's maintenance schedule and it also agreed with what I was doing. I had already made the decision to change the oil every 4 months and that is exactly what Mazda said, cool coincidence, it's almost like they KNEW! Well ya, they probably do. Anyway, that's my data point, guess you'll have to get a UOA for yours and see where the fuel dilution is to know how yours is going.
EDIT: Had to add.. with the fuel dilution that it has, the wear numbers have been excellent, been using Mobil 1 (adv full syn version) 5w30 in it.
I subscribe to 5K OCIs, but especially so on my friends 2019 CR-V. Dang thing thinks it's a Holley fuel dumper.
Elkins45
Site Donor 2026
Mazda says change the oil every four months?
Use 5W-30 and change in six month intervals. That will eliminate all concern. That's what I'm doing with my fuel-diluting Honda 1.5T Civic. No worries.
Is your Ford Fusion a 2.5 ? If it does, its port injected.
You don't have Direct Injection so naturally you would not have the fuel dilution results that some DI engines do.
Even if so, it would likely be the Ford Duratech 2.5 (also an excellent engine), but certainly not Mazda's SkyActiv 2.5.
No harm in going to 3k OCIs.
Let's not go there. "Upping the viscosity" is the kind of crazy talk that will have your children put you in a home sooner.
I'm a geezer, too. Just a couple of car lengths behind you.
My mazda has fuel dilution. When my wifes work trip was 4 miles each way. I ran Mobil 1 0w-40 especially in winter and changed it at 2k.
Now that its not short tripped like that, I am running High Performance Lubricants 5w-30 No-VII PCMO. I just posted a 10k oil sample that was very good, even with fuel dilution of 3%.
5 months or 5k miles whatever comes first. If doing a fair amount of short trips, I'll cut the distance interval by 50%.
Yes, in the owner's manual for the 2016 CX-5, page 6-9, under severe driving condition maintenance for USA residents, it says at 4months or 5k miles, replace the engine oil. Also same recommendation for severe driving in Canada, 4 months.
Similar threads
