Can Not Using 5W-20 Ruin Your New Ford Engine

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Feb 10, 2003
A friend of mine recently bought a Mercury Marquis. Ford/Mercury has a one hour class of instruction for new Mercury owners. Anyway, at this class, they were told to be careful of quick change places that might not use the called for 5W-20 weight oil. They said using a different weight such as 10W-30 would ruin the engine over time. Is there anyway there is any truth to this?

Can not using 5W-20 in the new Ford engines ruin the engine?

[ March 09, 2003, 07:10 PM: Message edited by: Americanflag ]
You'll also hear the argument that using the 5w-20 will ruin your engine.

Too thick? Too thin? What's a poor Ford/Lincoln/Mercury owner to do?
Ford gives you a class for Mercury owners...HA...they send Jeep owners to Jeep College(near Toronto)..this is where you get to beat the snot outa a new Jeep that D/C owns
I was expelled
...they never mentioned anything about oil and filters so I was bad in class
There is no way running 10w30 is going to kill a new Ford engine. When the engine is new, it won't hurt to run 5w20 either. Oil analysis results we've seen here have proven it. As the engine ages, you can safely step up in viscosity as you wish.
Geez all Volvo gives you is a child seat class (if you're lucky!)....

But - oil talk and demo bashing? WOW!

There is no way a good 10W-30 is gonna croak a sound engine - maybe inside the artic circle with dino....I agree with Pat, Man.
I think the only real issue one needs to consider about 5W20 oil or using some other weight, is warranty coverage. I've had Ford dealers answer that one on both sides of the fence. Don't know about Honda. It's probably a personal decision for the vehicle owner while the warranty is in effect.
I agree with Patman and Pablo, a 30wt. won't do anything to your engine. In fact, I myself probably was running a 20wt. oil @ 6k mile drains with trisynthetic for the last 80,000 miles, along with many other Mobil 1 users. Could there have been less wear on my engine if I ran a heavier 30wt.? Doubt it based on the fact 20wts. are getting the green light and will be the oils of the future. Jury is still out on this due to limited data though. If anythig, your getting better protection with a 30wt. oil. My wife's Focus has had 30wt. Amsoil in it for the last 6 months and it runs great. If your going to stick with the 20wt. I'd use a synthetic just for the security. Motorcraft is good stuff too from what I've read on here. Now F-150's are a different story. I would not run a 20wt. in a truck....I know it's probably fine but something about it just doesn't sit right with me on that.

[ March 09, 2003, 09:18 PM: Message edited by: buster ]
I, too, take the position that a decent 5W-30 or 10W-30 oil (presuming either or both would be considered an appropriate choice for the prevailing seasonal temperatures in your area in past years) would not harm your new Ford engine. However, the 5W-20 oils are showing good wear numbers and resistance to shear on the oil analysis reports trickling in, so they're apparently not a bad choice, either. Ford's been making engines longer than Carter's been making little pooper pills and I would venture that their engines are statistically as trouble free, overall, as anyone's. But, the occasional defective one does show up. So, the real problem, if I might use a baseball analogy, is being called "out" on a controversial warranty "pitch" in the event of engine mechanical trouble if the dealer or Ford pulls an oil sample and has it analyzed. You need to understand that the "opposing team", Ford and the dealer, are also the "umpire staff". I readily concede the point that it's YOUR car, and Ford's decision to require 5W-20 oil is probably arbitrary and based solely on milking a few tenths of a percent more in the CAFE numbers. But, until your powertrain warranty expires, it might be prudent to evaluate carefully the potential personal financial impact of using a non-specified engine oil.

[ March 09, 2003, 09:55 PM: Message edited by: Ray H ]
just one time I wish someone would give us a specific reason why we have to use 5w-20, instead of just saying it will ruin your engine. Please tell us that the oil filter is designed for 5w-20, the oil pump is designed for 5w-20, the top end needs oil as early as possible upon start-up, just one reason is all I ask from these doom & gloom oil fortune tellers. One guy on a website I visit frequently said our cams would wear out in no time if we didn't use 5w-20 oil (on my 2002 Honda Civic). I've heard the argument that engine tolerances are much tighter now compared to past years. Well I've compared the tolerances and specs on my 2002 engine to my old 1999 engine , and I've even gone far back as 1992 and guess what ?, the engine tolerances used by Honda have not changed since at least 1992. So that argument goes out the window. If someone is able to give us a good reason for using 5w-20 I'll be waiting patiently.
I don't see what all the fuss is about the warranty implications of this. Lets say you use 5W-30 and a year or so down the road you have engine problems, then just drain and refill with 5W-20 right, I mean even if the engine don't start, when they drain and analyze the oil its going to spec out at 5W20, even though it may have a little 5W-30 in it. Am I missing something here?
The reason Ford went to 5w20 oil was for a slight increase in fuel economy (less than 1% according to the bottle, if I remember correctly). They now recommend it for many older vehicles which originally specified 5w30 oil. They had a list of vehicles approved for the new 5w20 oil at the dealer last time I was there.

Speaking only of the F-150 engines, there were NO engine changes when the recommendation was changed to 5w20. The ford dealer my dad gets his oil changed at does not even use the 5w20; they put 5w30 in his truck even though it officially calls for 5w30.
I called Mobil 1, and they said to run their 5W-30, even over their new 0W-20. That made me go with the the 5W-30.
i figure, the companies may think oils are so advanced today, a 5w20 can perform well.

also, they may only make a 1 percent increasein MPG, but imagine that 1 percent in millions of cars... probably saves LOTS of gas!

although, i wouldnt run a 5w20, maybe mobil 1 0w20
I do think it's a good idea to use an oil that will easily flow during the warmup period in an OHC engine. So my first choice for one of these would be 5w-20/0w-30 or 5w-30, even for a fairly warm climate.

I think of it this way...a 5w20 is MUCH thicker cold than a 5w30 is when hot. So I don't see how a 5w30 could hurt the motor. The 5w20 may flow a bit faster at start-up, but if there were no significant engine design changes from 2000 to 2001 it's moot. The warranty issue is tricky and will likely differ between dealers. I'm using 5w30 in my 2002 3.0 Ranger because that oil worked just fine in my '92 and '97 3.0's.
5W-20 is thinner than 5W-30 when cold, and also thinner than 5W-30 when hot.

Yes they're both 5W's but look at the specs!

BTW the only reason why these oil analysis look so good is because everyone's using semi-synthetic 5W-20 or full synthetic 5W-20 and NOT dino 5W-20.

Meanwhile for 5W-30 we get to see reports of dino and synthetic.

If you want a fair comparison i suggest comparing full synthetic 5W-20 with full synthetic 5W-30, i.e. a M1 20wt and a M1 30wt.

Otherwise don't compare 5W-20 to dino 5W-30 in terms of UOAs.

). I've heard the argument that engine tolerances are much tighter now compared to past years. Well I've compared the tolerances and specs on my 2002 engine to my old 1999 engine , and I've even gone far back as 1992 and guess what ?, the engine tolerances used by Honda have not changed since at least 1992. So that argument goes out the window. If someone is able to give us a good reason for using 5w-20 I'll be waiting patiently.

I've also compared the specs on several vehicle engines over the last 10-15 years. THERE IS NO DIFFERENCE! The rod, cam and main bearing clearances are the same. Cylinder wall to piston clearances are the same. There has to be a certain amount of space between mating surfaces for the oil film to flow, and to compensate for expansion/contraction cycles. This hasn't changed over the last few decades. The argument about today's engines being machined more precisely is simply untrue.

The only reason to use a lighter weight oil is for better CAFE averages (as has already been stated). Why can't the auto makers just tell the consumer that, and quit trying to insinuate that their product is now more "precisely" made?
Mike, how you do figure a 5-20 is thicker cold than a 5-30. They are both 5 weights and will be relatively the same thickness at the required temperature to make the grade by SAE. I believe it's -30 C.
Hey guys;

Mike said:

I think of it this way...a 5w20 is MUCH thicker cold than a 5w30 is when hot.

So, The folks who say that using a 5w-30 will KILL the engine because it's too thick when cold and that is why you must use 5w-20 are full of it.

Is not 5w-20 thicker COLD than 5w-30 when it's hot? If it is, how can 5w-30 hurt the engine?? (or that's how I'm reading what Mike said...)

A little off topic..

I decided to go to the new owner "class" with my sister (she bought a 2003 Ford Taurus) and got to ask questions to the "expert" on the care of her car. When it was all over, it comes down to this;

Take your car to Ford and have them do all maintence incl oil changes. They know your car better than anyone. Also, if the manual states something, do it.
(oh, and if the car starts to overheat, pull over and STOP the engine ..smartest thing I heard the whole night )

Then, I asked the expert if I could get a sample of the oil (bulk systems deliver to each station) for UOA, He declined as he did not know how to turn on the pumps.. (They are air activated) I asked if I could see the drums. Not allowed.
I'd bet I'd see some 5w-30 tags or 10-30 label on drums like the local Honda dealer. My Dad's 2001 honda gets 10-30 Quaker State for his oil changes FROM THE DEALER even though it's states 5w-20 in the manual.

I asked him why my manual states 5w-30 in my Taurus and my sisters has 5w-20. It's due to changes in the engine. Both have the same engine. Then I asked him why I got a letter stating that I should run 5w-20 now. Same engine (well, It's got new heads since the 61k mile gaskets let go) and he stated that the 5w-20 is better oil than 5w-30.

I don't know, But my 5w-30 oil is going to 20 wt in 3000 miles, What would 5w-20 do?

At least I'm getting better protection while the 30 wt oil is going to 20 wt!

Cheers! Bill

Yes I'm considering Group III 5W-20s are Synthetic blends.

So far, I cannot find a true dino 5W-20 (Group II+) - only "synth blends" or Group IIIs and upcoming PAOs/Group IVs.

BTW Mercon-V is a Group III ATF but most regard it as synthetic blend.

Anyhow - of course a synth blend will tend to look better on a UOA compared to a dino 5W-30. A better comparison would be a group III 5W-30 vs. a group III 5W-20, or a group IV 5W-30 vs group IV 5W-20.

Notice how all 5w-20s cost more than 5W-30 dino.

5W-20 is thinner when cold and when hot than 5W-30.

[ March 10, 2003, 01:30 PM: Message edited by: metroplex ]
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