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Switching Engine Oil after 100k miles

12K views 19 replies 7 participants last post by  222speed3 
#1 ·
I've been using Ford Motorcraft 5w20 syn blend & 910S filter for the past 5-6 years, 102k miles. I know there are a lot of opinions about motor oil but this oil has met my requirements (reasonably priced and always locally available).

I have the hunch that I should be switching my oil at this mileage, but I've always been a firm believer in not switching oils as the engine gets "used to" what you put in it.

That being said, what is the general consensus here on switching oils? I'm seriously considering this Catrol GTX Magnatec 5w20 full syn as my commute is 10mi, 20min so my engine is hardly running the way it was for the past 5 years when I had a 50mi, 1.5hr commute.
 
#2 ·
In the distant past, bad things may have happened as a result of switching from one brand or type of oil, to another brand/type. But we're a solid 15 years removed from that. The synthetic compounds/additives used in oils have come a long way in the past 30 years. Ditto engine seals.

Worth worrying about on a car that's 15 or more years old. Otherwise, don't worry.

PS. Assumes your engine is running well with no issues/leaks.
 
#3 ·
What I'd recommend is to have Blackstone run a used oil analysis after your next oil change...the results (and their explanation of what the numbers mean) will give you a clearer picture of how well your oil has been working for your engine, and if you need to switch.
 
#5 ·
Hey Doc. I've never had an oil analysis done. Cynics say its a waste of time and money. I mean if your MPG is fine, and there's no burning/loss, why do it? I can be convinced, just asking some questions.

When they send the results, do they also include detailed recommendations? And if you send them oil that you used all winter, does that necessarily mean the data is applicable to what you should use in summer? I'm old school, I use a different weight in late spring/summer/early fall vs winter (5w30, vs 5w20). I believe that when the sub freezing temps are gone, you want 5w30.
 
#8 ·
I think I remember reading some of the non NA 3s were coming with 5w30 out of the factory at some point. Not sure if it was the same engine though.

I wouldn't change weights. I've been running 5w20 for over a 100k miles, why would I want to make my engine work harder running a more viscous oil? I won't argue that 5w30 provides more protection because it is more viscous but it could cause some issues outside of decreasing gas mileage.
 
#9 · (Edited)
I think I remember reading some of the non NA 3s were coming with 5w30 out of the factory at some point.
I've read that also.

I won't argue that 5w30 provides more protection because it is more viscous
That's it. And I've seen plenty of data which says 5w30 flows just as well as 5w20 at start up, except in extreme cold (many degrees below freezing).

If you're interested in reading debates on this (there must be 10,000 of them kicking around on the web), these two are as good as any:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2884476

http://boards.straightdope.com/sdmb/showthread.php?t=568173
 
#10 ·
Yea I am a big fan of Bob's website, personally.

They should flow just as well at start up, even in extreme cold as the 5(winter) weight is the same... or one would think.

I did swing by Walmart during lunch and saw they have the Castrol GTX Magnatec 5w20 full syn for $20/5qts. That price is ridiculously low for a full synthetic. I also noticed that the same Magnatec oil is a semi-syn at the 5w30 rating.

I won't argue with anyone who runs 5w30 especially if they live in a warmer climate and have their car on the highway for long stretches of time. I just think for my personal situation which is short trips on back roads in NE US it's not necessary.

I know the reason Mazda went to 5w20 (as other manufacturers have) is because they thought the lower viscosity was sufficient and it gives them a few decimal points for fuel economy.
 
#12 ·
I did a lot of research and I think I'm going to give that Castrol Magnatec a shot as it seems to get pretty good reviews. Also $4/qt for a full synthetic 5w20 is hard to argue against.

I will try to remember to do an oil analysis on both the motorcraft and magnatec oils if I can, and post them in the appropriate forum (thx doc)
 
#14 ·
The only reason I do it is so I can mainly keep tabs on things. If an oil analysis goes south real fast, I know of it, and typically they can point you in the direction of what's going to happen. That's the only reason I do mine.

If they see wear on typical bearing materials, I can consciously begin to save money off to the side to pay for the cost. As opposed to obliviously going into it and spending money at just the wrong time.
 
#15 ·
This is pretty much the same reason I do them. I don't send a sample off after every oil change, just every 20-30k miles. I send an initial one off after the car has 5k miles on the odometer to see how engine break-in is doing, and if the oil I'm using seems to be appropriate. (One thing a lot of us learned from UOAs a few years ago was that while the NA 2.0 and 2.3 MZRs do great with Mobil 1 synthetic, the Speed3 motor hates it.)
 
#16 · (Edited)
I have an older version of a mazda factory manual for mazda 3 and mazdaspeed3. It actually says to use 5w-20 for the mazdaspeed. This was canged later on....wonder why. You would be a fool to use that in a FI ride. For low revving NA it would be ok.

I ran an acura before. My Wife still uses a honda civic. For honda's the spec for oil is 5w-30. Reason being is the high revving. The engine wear is more so you need 5w-30. For low revving engines you will be ok with 5w-20.

For me speed I use rotella 5w-40 because the 5w-30 still shears fast in a turbo app. Also need the extra viscosity for protection. Stuff is great for a speed. Does wear on your 02 sensors and cat more. Have OCC's to help with that.

http://www.bobistheoilguy.com/effects-of-shearing/

http://www.bobistheoilguy.com/putting-the-simple-back-into-viscosity/

Great stuff to read on this site.
 
#18 ·
...For me speed I use rotella 5w-40 because the 5w-30 still shears fast in a turbo app. Also need the extra viscosity for protection. Stuff is great for a speed. Does wear on your 02 sensors and cat more. ....

Rotella Diesel 5W-40 is an excellent choice for a Mazdaspeed engine in the summer for track use and someone who drives aggressively.

It will not affect your cat or O2 sensors anymore though. Diesel engine oil, like gas engine oils, do not have high levels of zinc or phosphorus anymore.
Modern diesel engines have catalytic converters, O2 sensors and particulate filters.
So current diesel engine oils do not have zinc or phosphorus either.


Not only are modern engine oils worse than older engine oils, running extremely light viscosity also makes for reduced engine longevity.

Reduced engine life is already common in many platforms.
But, as was mentioned, most folks lease their vehicles and this is not a factor.
 
#17 ·
Interesting links there. I haven't heard the low vs high rev consideration before. My wife's Honda CR-V spec'ed 0w20 full syn and was absolutely a low revving engine.

I like to open her up on winding back roads and play a lot in the 4500-6000+ rpm range. I don't ever redline the 2.0 but I have fun getting close on sporty drives.

Is that still "low revving"?
 
#20 · (Edited)
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