5w-20 in Older Engine? Ford 7.5L V8

Status
Not open for further replies.

92saturnsl2

Thread starter
Joined
Mar 2, 2004
Messages
3,663
Location
Kentucky
I've driven the truck about 400 miles since changing the oil, and I've observed two things: a) drop in oil pressure b) improved fuel economy The oil pressure gauge used to sit on the last hash mark before "H", and never budged. Hot, cold, winter, summer; it didn't matter. For a long time I thought it was just a dummy gauge, or "glorified idiot light." That was with 15w-40 or straight 30. Now after 30 minutes of driving, even at cruising RPM (3,000 rpm on the highway), it drops down to 3/4 and stays there. Might drop a tick down to about 2/3 at warm idle. Soon I will put a mechanical gauge on it and see what how the factory gauge corresponds to actual pressure. That'd be a whole lot more helpful than just "L" and "H" or somewhere in between smile My last run of both tanks gave me 10.54mpg. Before now, I haven't made it past the 10mpg mark, it would average about 9.5 mpg which is about 180 miles per tank. That's almost a ten percent increase, which I'll certainly take. Obviously I'll have to run a few tankfuls to get a true before vs after average, but my drive doesn't change (125 miles per day, Mon-Fri), so this looks promising. Nothing unusual noted such as increase in engine noise / NVH. Difficult to tell if it's improved cold starting at all, as it hasn't dropped down to the teens, or single digits where it would really labor to turn the engine over before. Time will tell on that one.
 
Joined
Feb 24, 2013
Messages
2,035
Location
Ontario, Canada
Pretty cool! Glad it's working out so far. If that factory gauge is anywhere near accurate, it may suggest a larger than average volume pump, which would be ideal for a lower vis. oil. Can't wait to see pressures from a mechanical gauge
 
Joined
Jan 6, 2013
Messages
523
Location
LaVergne, TN
Originally Posted By: abycat
I use 5-20 in my ford. Its on the 5 20 list from ford. The oil pressure is the same with 5 30. I also towed thousands of pounds in very hot city traffic for thousands of km with it in. Seems just fine to me. Im going to keep using it until I sell the truck in the future.
Ya can't tell pressure difference from the factory gauge.. It's a dummy switch it's up unless pressure dips below 4#'s of pressure
 
Joined
Sep 10, 2005
Messages
5,450
Location
Massachusetts
Originally Posted By: Ramblejam
Originally Posted By: Zaedock
Well, the '93 back spec is for an EFI engine vs. the '85 carb'd, so this post is irrelevant.
Familiar with the 460, I see? Hopefully you'll answer the question for us then, Zaedock. Either: A. Ford made across the board changes in their entire light truck engine line (4.9, 5.0, 5.8, 7.5) for 1993 with negates the usage of 5w-20 in earlier models. B. There's another reason that Ford selected 1993 as the beginning model year for a lighter engine oil.
I am familiar as I built and swapped a 460 into a Fox body Mustang many years ago. The short blocks (D9 castings) are virtually the same for the entire production run. The heads changed slightly in '93 as did the cooling system, which utilized an oil/coolant heat exchanger. Ford probably determined that the design allowed consistent oil temps allowing the use of 5W20. A real oil pressure gauge would be best for an absolute determination, but IMO 5W20 would probably be fine for any 460 in winter, if the carb version is well tuned.
 
Joined
Nov 11, 2010
Messages
9,779
Location
Saskatoon canada
Originally Posted By: Merkava_4
Originally Posted By: 92saturnsl2
Because of the flat tappet cam, I had QS Defy 5w-20 in mind, with a pint of STP Oil Treatment for a little extra ZDDP. QS Defy should be a heavy 20 weight if I'm not mistaken.
The best way to wipe out that camshaft (besides filling the crankcase up with transmission fluid) is to run 5W-20 oil in the engine. But you already knew that - you're probably tired of the old truck - time to get a new one right?
Truly absurd. I'm disappointed that with as long as you've been here nothing has been absorbed. OP. If you've got leaks already I suggest fixing them. If fixing them isn't an option I suggest liqui-moly motor oil saver. If the gasket isn't physically broken that stuff will help curb the flow. Now forget the stp. That stuff has less ppm of zddp than SN grade oils do so you'll be diluting the zddp and making the oil weaker,and the stp will thicken the oil which turns it to a 30 grade which defeats the purpose of going thinner in the first place. As far as zddp goes if your engine is stock the spring rates aren't high enough to require extra zddp and the engine isn't new,so the cam is already work hardened so there is no need for any extra zddp anyways. Extra zddp is only required during break in because the cam is newly milled and "soft". Once you get the new engine heat cycled the cam has "work hardened" and extra zddp is no longer required. And zddp is caustic. Engine oils add elements to help neutralize the caustic nature of zddp,so blindly adding it will help compromise gaskets faster as well as pit metal. I've always been a thicker is better guy however since finding bitog I've had to teach myself to expand my comfort zone. What I've learned here is that no one oil fits all and ambient temps,running conditions and how hot the engines going to operate all play a role in oil choice. If your truck is in sound mechanical shape then try a 20 grade. Monitor all the gauges very closely and go from there. Let's remember that when your truck was manufactured 5w-30 grade engine oils weren't very shear stable and they turned into 20 grades pretty quickly in service. So I doubt very much any harm will come to your big block using one. I do suggest either adding motor oil saver,found at napa,or using a high mileage 5w-20 to maybe help the gasket leak. Or fix it and be done with it. I also suggest having a quart or 2 of a 40 grade diesel oil with the truck. If you find that the 20 grade is being consumed rather quickly you can thicken it up with the thicker oil and monitor consumption. My personal recommendation is M1 0w-40 or devlac elite 222 0w-30. The 0w will help pump fast and lessen fuel consumption during warm up. They tend to stay in grade and if fuel dilution(carb) does present itself you've got a bit of viscosity in reserve,a nice thing to have especially once you hook a trailer up to it. I drove an 88 5.0 high mile mustang around all summer with 5w-20 and I felt right away the engine had more pep and throttle response. Oil pressure while driving was a pound or 2 lower so that was no biggie b And thinner oil dissipates heat faster. It also warms up faster. So consider that being a benefit while towing,right? If your gonna go thinner get something to slow the oil leak or its gonna get worse. I liked defy 5w-20. I used it I'm my ram hemi last year. I towed a trailer loaded with a car all over the western provinces last spring using that oil and the truck ran stellar. So to summarize I say go for it,but monitor closely until you're confident in the selection
 
Joined
Sep 3, 2010
Messages
3,495
Location
VA
Originally Posted By: Flareside302
Originally Posted By: abycat
I use 5-20 in my ford. Its on the 5 20 list from ford. The oil pressure is the same with 5 30. I also towed thousands of pounds in very hot city traffic for thousands of km with it in. Seems just fine to me. Im going to keep using it until I sell the truck in the future.
Ya can't tell pressure difference from the factory gauge.. It's a dummy switch it's up unless pressure dips below 4#'s of pressure
Before 1990 Ford had real gauges that actually respond to pressure change...
 

92saturnsl2

Thread starter
Joined
Mar 2, 2004
Messages
3,663
Location
Kentucky
Originally Posted By: Miller88
That's a lot of miles! and gas. Do you need to drive the truck for that long commute?
Well sorta.. I'd been planning to sell my car for awhile now, and picked sooner rather than later. I was able to sell it recently with a little bit of equity, whereas if I kept driving it for another few months, I'd likely be upside down on the value because of the mileage. I'd put 125k on in 4 years. I'm moving closer to work and buying a new car when tax season rolls around, so this high mileage commute will go by the wayside. As of right now, it's nearly $800 a month in fuel, but only until February which I can handle.
 

92saturnsl2

Thread starter
Joined
Mar 2, 2004
Messages
3,663
Location
Kentucky
Originally Posted By: Clevy
So to summarize I say go for it,but monitor closely until you're confident in the selection
Appreciate the helpful insight. Too late to go back on my oil choice, as Defy 5w-20 is already in the crankcase. I did omit the STP additive upon recommendation of BITOG members. As far as an oil leak goes, I've tackled pretty much any and all maintenance items: valve cover gasket, front seal, timing chain (and front cover gasket), ignition components, belts, carb rebuild, etc. EXCEPT items which require significant engine teardown.. That means the oil pan was tightened but gasket not replaced (it doesn't leak there anyways) and rear main seal. Tune is next to perfect IMO (compression checks out okay too), it literally runs and drives as smooth as any newer truck I've driven. Just eats a lot more gas with a big block roaring away at 3k RPM going 70mph. Needs an overdrive tranny something fierce. I suspect the rear main may have a slow leak, but I can't confirm it because the undercarriage is so thickly coated from years of the oil cooler / filter adapter leaking and nobody noticing it until I bought the truck. One O-ring and tightening up the filter adapter fixed 95% of my oil loss literally overnight. Needless to say, I can live with the 1qt every 2-3k it is consuming or leaking; it is a 29 year old truck after all. Engine teardown and rebuild will come some day down the road, but not at the moment as it's my daily driver for the next couple months. I will however heed your advice and keep a close eye for extra consumption. I've always been the type to check my oil at every fill-up and keep a close eye on gauges. Can't ever be too cautious. I'll update as I get a better average for fuel economy, as well as oil pressure when read with a mechanical gauge.
 
Joined
Jan 6, 2013
Messages
523
Location
LaVergne, TN
Originally Posted By: TFB1
Originally Posted By: Flareside302
Originally Posted By: abycat
I use 5-20 in my ford. Its on the 5 20 list from ford. The oil pressure is the same with 5 30. I also towed thousands of pounds in very hot city traffic for thousands of km with it in. Seems just fine to me. Im going to keep using it until I sell the truck in the future.
Ya can't tell pressure difference from the factory gauge.. It's a dummy switch it's up unless pressure dips below 4#'s of pressure
Before 1990 Ford had real gauges that actually respond to pressure change...
Yes.. He has a 94 listed in his sig... The guy in responding too... Not OP...
 
Joined
Jan 6, 2013
Messages
523
Location
LaVergne, TN
Being your in Colorado is go with M1 0w40.. Those 460s don't care really what oil, but with the amount of miles on it I'd definitely go 40.. 10w30 was factory spec'd weight..
 
Joined
Jan 27, 2003
Messages
1,836
Location
Pac NW
Originally Posted By: Ramblejam
http://www.ford-cruising.hu/miscimages/0219.pdf "Approved For SAE 5W-20 Motor Oil: 1993-1998 7.5L All Vehicles" Of course, that's just an official document from Ford. What do they know, right? smirk
Of course, the OP's F250 is "a carburated 1985..." DUH. p.s. to the OP: Is "almost 10%" worth trashing the engine? Don't you think 9.5-10mpg is about right for a 460 pushing 30? I use (almost)FAR dino 10W-30's because that's what big block carb'ed Fords were designed to use. Good luck: hope the person you sell it to gets a truck that lasts as long as the one you purchased...
 
Last edited:
Joined
Mar 31, 2010
Messages
6,015
Location
Iowa
Originally Posted By: Norm Olt
Originally Posted By: Ramblejam
http://www.ford-cruising.hu/miscimages/0219.pdf "Approved For SAE 5W-20 Motor Oil: 1993-1998 7.5L All Vehicles" Of course, that's just an official document from Ford. What do they know, right? smirk
Of course, the OP's F250 is "a carburated 1985..." DUH. p.s. to the OP: Is "almost 10%" worth trashing the engine? Don't you think 9.5-10mpg is about right for a 460 pushing 30? I use (almost)FAR dino 10W-30's because that's what big block carb'ed Fords were designed to use. Good luck: hope the person you sell it to gets a truck that lasts as long as the one you purchased...
Why is it that everyone seems to be glossing over the fact that a 20 grade oil is listed as fine for use in his manual? Reading comprehension? Also, can you tell me what separates a thick 20 from a thin 30? Or what's the difference between a cool 20 and a hot 30? Bet you'd be hard pressed to tell. Ford allowed the use of a 20 grade oil in the wintertime and did not make the distinction of miles driven. They knew the oil would be plenty cool and therefore still provide proper lubrication.
 
Joined
Dec 12, 2002
Messages
43,686
Location
'Stralia
Given that to all intents and purposes there is no difference between the 20 and 30 (I DO get that they overlap, neither you on I do know where this engine is operating at)...do you think the 10% economy is : a) possible; b) going to be sustained; c) an aberrant statistic. ?
 
Joined
Apr 9, 2008
Messages
15,883
Location
Central NY
Originally Posted By: The_Eric
Originally Posted By: Norm Olt
Originally Posted By: Ramblejam
http://www.ford-cruising.hu/miscimages/0219.pdf "Approved For SAE 5W-20 Motor Oil: 1993-1998 7.5L All Vehicles" Of course, that's just an official document from Ford. What do they know, right? smirk
Of course, the OP's F250 is "a carburated 1985..." DUH. p.s. to the OP: Is "almost 10%" worth trashing the engine? Don't you think 9.5-10mpg is about right for a 460 pushing 30? I use (almost)FAR dino 10W-30's because that's what big block carb'ed Fords were designed to use. Good luck: hope the person you sell it to gets a truck that lasts as long as the one you purchased...
Why is it that everyone seems to be glossing over the fact that a 20 grade oil is listed as fine for use in his manual? Reading comprehension? Also, can you tell me what separates a thick 20 from a thin 30? Or what's the difference between a cool 20 and a hot 30? Bet you'd be hard pressed to tell. Ford allowed the use of a 20 grade oil in the wintertime and did not make the distinction of miles driven. They knew the oil would be plenty cool and therefore still provide proper lubrication.
It seems a lot of people are missing that ... I don't think it'd be a problem. Even on a carb that might dillute fuel - he's running it down the highway at 3000RPM. No doubt, it gets up to temperature and "burns" off the excess fuel!
 
Last edited:
Joined
Dec 5, 2009
Messages
28,089
Location
Regina, Saskatchewan, Canada
Originally Posted By: The_Eric
Why is it that everyone seems to be glossing over the fact that a 20 grade oil is listed as fine for use in his manual? Reading comprehension?
I read it just fine. I was buying oil in 1985. I don't remember seeing a lot of (actually any) 5w-20 on the shelves. This wouldn't be the only manual with a bit of a phantom recommendation. There certainly were 20 grades available, but exceedingly rare. I bet that if everyone who used a 5w-20 in a 460 in 1985 by some fluke had an engine failure and they were all covered by Ford, Ford would have barely noticed, given how rare the grade was. Manuals are good resources. But, sometimes they recommend 40 grades with ILSAC certifications, too, or a conventional 5w-40. My beef in this discussion is that I don't see the benefit. The fuel economy savings wouldn't outweigh the risk in my mind. While the manual allowed for a 5w-20, we also have to remember that recommendation disappeared in subsequent years, then reappeared. It's probably not going to hurt a thing, but there are other ways to save fuel.
 

OVERKILL

$100 Site Donor 2021
Joined
Apr 28, 2008
Messages
53,087
Location
Ontario, Canada
Originally Posted By: The_Eric
Also, can you tell me what separates a thick 20 from a thin 30? Or what's the difference between a cool 20 and a hot 30? Bet you'd be hard pressed to tell. Ford allowed the use of a 20 grade oil in the wintertime and did not make the distinction of miles driven. They knew the oil would be plenty cool and therefore still provide proper lubrication.
HTHS.
 
Joined
Dec 12, 2002
Messages
43,686
Location
'Stralia
Originally Posted By: Garak
Originally Posted By: The_Eric
Why is it that everyone seems to be glossing over the fact that a 20 grade oil is listed as fine for use in his manual? Reading comprehension?
I read it just fine. I was buying oil in 1985. I don't remember seeing a lot of (actually any) 5w-20 on the shelves. This wouldn't be the only manual with a bit of a phantom recommendation. There certainly were 20 grades available, but exceedingly rare. I bet that if everyone who used a 5w-20 in a 460 in 1985 by some fluke had an engine failure and they were all covered by Ford, Ford would have barely noticed, given how rare the grade was. Manuals are good resources. But, sometimes they recommend 40 grades with ILSAC certifications, too, or a conventional 5w-40. My beef in this discussion is that I don't see the benefit. The fuel economy savings wouldn't outweigh the risk in my mind. While the manual allowed for a 5w-20, we also have to remember that recommendation disappeared in subsequent years, then reappeared. It's probably not going to hurt a thing, but there are other ways to save fuel.
This thread has been wandering in and out of my thoughts for days, and I'm starting to question what the ambient temperature recommendations actually mean... The University 101 has one thing right, and that cars have thermostats...so when the vehicle is tooling down the highway, the engine is at temperature (thermostat design aside), regardless of ambient. I'd be happy with a 20 in said engine if I was planning to and from work, not so on a long highway, and not towing, regardless of the range in the manual, and the outside temperature.
 
Joined
Sep 3, 2010
Messages
3,495
Location
VA
Originally Posted By: Shannow
This thread has been wandering in and out of my thoughts for days, and I'm starting to question what the ambient temperature recommendations actually mean... The University 101 has one thing right, and that cars have thermostats...so when the vehicle is tooling down the highway, the engine is at temperature (thermostat design aside), regardless of ambient. I'd be happy with a 20 in said engine if I was planning to and from work, not so on a long highway, and not towing, regardless of the range in the manual, and the outside temperature.
Very true but when one is tooling down the highway, the oil pan hanging down in a 0*F breeze does become a fairly efficient oil cooler that's not referenced coolant temp...
 
Joined
Apr 9, 2008
Messages
15,883
Location
Central NY
Originally Posted By: Garak
Originally Posted By: The_Eric
Why is it that everyone seems to be glossing over the fact that a 20 grade oil is listed as fine for use in his manual? Reading comprehension?
I read it just fine. I was buying oil in 1985. I don't remember seeing a lot of (actually any) 5w-20 on the shelves. This wouldn't be the only manual with a bit of a phantom recommendation. There certainly were 20 grades available, but exceedingly rare. I bet that if everyone who used a 5w-20 in a 460 in 1985 by some fluke had an engine failure and they were all covered by Ford, Ford would have barely noticed, given how rare the grade was. Manuals are good resources. But, sometimes they recommend 40 grades with ILSAC certifications, too, or a conventional 5w-40. My beef in this discussion is that I don't see the benefit. The fuel economy savings wouldn't outweigh the risk in my mind. While the manual allowed for a 5w-20, we also have to remember that recommendation disappeared in subsequent years, then reappeared. It's probably not going to hurt a thing, but there are other ways to save fuel.
I think it was straight 20; SAE20. Not 5w-20.
 
Status
Not open for further replies.
Top