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Oil Question

Got a 91 F250 with the 351W about 140000 miles on it. The previous owner used 5w-30 synthetic blend oil with Lucas additives. When I go to change the oil should I stick with that or just go full synthetic?

Thanks
idcwby
 

Fellro

Moderator
Staff member
It depends more if they stuck to a certain brand, and if it was for a long time or not. Generally, today's oils aren't near as bad as it used to be about switching around.
 
I'm the third owner that I know of. The guy I got it from had a shop do all the work so I know they used the same oil every time. Just don't get why you would run a blend instead of going full synthetic.

Thanks
idcwby
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
The preferred weight would be whatever is printed on either the cap or the sticker on the radiator core support. After that, a Motorcraft filter and your favorite brand of full synthetic or dino oil. Skip the extra bottled stuff and IMO, skip any semi-synthetic oil. Why skip the semi-synthetic? Because they don't tell the consumer what percentage is syn and what is dino. Therefore, 1/8 oz of synthetic in 31 7/8 oz of dino and viola, semi synthetic oil and to claim that semi-synthetic name cost near nothing.

Generally, today's oils aren't near as bad as it used to be about switching around.

X2 on this one. Add to that, breaking the old 3,000 mile oil change spell for normal, daily usage.

Edit: There is a really great resource that's all about oil, that interweb site would be bobistheoilguy.com
 
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fatherdoug

Tonto Papadapolous
^^^Agreed. To me, the only advantage of buying semi-synthetic would be cost. I would just do one or the other. I know my '89 460 lists 10W-30 as recommended oil. Did things change in '91?
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
^^^Agreed. To me, the only advantage of buying semi-synthetic would be cost. I would just do one or the other. I know my '89 460 lists 10W-30 as recommended oil. Did things change in '91?

His may call for 10W-30 given the vintage of vehicle. However, somewhere along the way Ford put out a TSB advising acceptable usage of, IIRC, 5W-30 in some engines and model years. That or another TSB that stirred the pot by advising acceptable usage of 5W-20 in some engines and model years. Easy enough to look up the TSB by simply going to bbbind.com and reviewing it.
 

LEB Ben

Arrogant A-hole At-Large
34,919
1,124
outside your house
Here's the thing that gets me, so bear with me.

1) I've used top shelf and done OCI's sooner than recommended. I've literally used ATF for 20,000 miles. I've let an oci go 40k before...and everything in between. I still get 250-300k out of gas engines, regardless of treatment. I also send my stuff off to get analyzed at Blackstone, and every single time, there's still life left at 20k regardless of what's used. So, my take...as long as you're not breaking in an engine, the engine doesn't care what you use, as long as it's not metal on metal and it's filtered. I do religiously swap filters.

2) I have no idea where the 3,000 mile OCI recommendation came from...I have lit going back to the 50's through the 90's showing anywhere from 7-12k (or once a year), and my 2000's lit is showing upward of 15k.

3) I have lit from the 50's-2000's showing different recommended oils to be used depending on climate and driving conditions...usually ranging somewhere between 0w20 and 15w40 (not all for the same vehicle).


So that being said...I personally believe, it doesn't matter as long as it's lubricated. If spending more gives you more peace of mind, go for it.
 

fatherdoug

Tonto Papadapolous
Agreed, Ben. My personal experience goes with 3000 mile intervals for two reasons.

1) Most of our mileage is 4 miles or less, thus causing buildup of moisture.

2) We still use wagon trails for roads out here. I change the air filters every 6000 miles, because it needs it.

This is NOT for everyone, but it works for me.
 

LEB Ben

Arrogant A-hole At-Large
34,919
1,124
outside your house
Agreed, Ben. My personal experience goes with 3000 mile intervals for two reasons.

1) Most of our mileage is 4 miles or less, thus causing buildup of moisture.

2) We still use wagon trails for roads out here. I change the air filters every 6000 miles, because it needs it.

This is NOT for everyone, but it works for me.

Yeah...if a rig has been sitting for a while, or was driven through a creek or some kinda harsh extreme, I'll generally change the oil with no real regard to miles on it. There are always extenuating circumstances, and you have to do what you're comfortable with.
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
My personal experience goes with 3000 mile intervals for two reasons.

1) Most of our mileage is 4 miles or less, thus causing buildup of moisture.

2) We still use wagon trails for roads out here. I change the air filters every 6000 miles, because it needs it.

This is NOT for everyone, but it works for me.

^^^ That type of driving is covered in the maintenance manual under severe duty, making it fair game for 3K or probably once a year, whatever comes first. ;) The reality is, if a guy does his homework and reads into it (and it'll take some time and effort), oil performance has improved vastly over the last 10-15 years. The validation comes from a UOA from Blackstone, and for a vehicle used as a DD under normal conditions (doesn't mean the air is always dust free) don't be surprised to see people send in samples (full synthetic) with 15K on the oil, and the test results show there was life left. You can learn a lot about an engine and the additives in from UOA, and for that matter UOA isn't just limited to engine but it's good for the tranny and if one really want to know, the X-fer case and axles and heavy duty trucks (semi, wheat truck, moving truck, etc) are also fair game.
 

fatherdoug

Tonto Papadapolous
True, Bill. When I worked for the power company, I was good friends with the guy that ran the PDM group(Predictive Maintenance). One of their jobs was collecting oil samples for analysis that was sent to an oil analysis lab in Spokane. I don't remember the name. On Edit, the lab was called OSI.

The oil analysis usually came back high in moisture. A long trip to Billings and a resample with the same oil showed moisture levels in the acceptable range.

When Mobil Oil started providing analysis free of charge if we bought our lubricating oil from them, I sent one in and the analysis lab told the PDM guy that the oil was not a Mobil product. Thus, the freebies stopped. :(
 
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polarbear

just growing older not up
12,878
607
Boring, Oregon
Got a 91 F250 with the 351W about 140000 miles on it. The previous owner used 5w-30 synthetic blend oil with Lucas additives. When I go to change the oil should I stick with that or just go full synthetic?

Thanks
idcwby

I've used Motorcraft 5-20 blend in my last six Ford products (2 F150's, 2 Grand Marquis, a Sable, and a Taurus). 315K miles on one F150, 275K on the second, 100K miles on the first Marquis, 210K miles on the second, 140K miles on the Sable, and now 146K on the Taurus. Oil changes every 5-7K miles with a filter. None of those vehicles used a quart of oil between changes.

There may be better products on the market, but I'm sticking to the old redneck saying "don't fix what ain't broke."
 

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