Fox oil change

rad4lif

Member
Mar 1, 2019
22
1
13
44
LA
i own 90 5.0 foxbody with basic upgrades i got close to 200k miles i’m running regular oil on it...my question is...i’m planning going with synthetic oil what is recommended to use n what grade...??
 
  • Sponsors(?)


FastDriver

My dad had a bra
SN Certified Technician
Sep 5, 2001
4,543
1,247
214
Fort Knox, KY
Too late to switch. You will create leaks you don't have as the synthetic works like a detergent. Can also dislodge sludge that could find its way to worse places. At least, this is what I've been told.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
16,940
5,415
193
polk county florida
  • Like
Reactions: Potomus Pete

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
33,092
9,229
224
Massachusetts
I switched to synthetic a couple years ago. Nothing bad happened, and no leaks.

Mobil with a Motorcraft filter. Same viscosity as original.
 
  • Like
Reactions: Habu135

1990 5.0 LX

Member
Apr 11, 2019
37
21
18
70
Ben Lomond, CA
I disagree with the comments on switching to synthetic oil. My '90 LX has 320K miles and I switched to 10w/30 Castrol synthetic at 225K miles. No smoke, no leaks. I think that's an old wives tale. At the last oil change, I switched to Mobil 15W/50 synthetic on the advice of my mechanic since it's obviously an older motor.

The argument for synthetic versus regular oil is synthetic reduces friction in the motor and increases motor lifespan. A while back in Mustangs and 5.0 magazine they had a dyno test which demonstrated that switching to synthetic added 5 hp on average at the rear wheels. That's clear proof of friction reduction.

Go with synthetic, you'll be glad you did.
 
  • Like
Reactions: My92cashtrap

Blown88GT

Founding Member
Nov 13, 1999
2,041
468
134
Palm Beach Gardens, FL
I tried synthetic about 25 years ago with maybe 40k miles & it leaked out everywhere, including the new supercharger.
I went to the blend a few years ago along with a seal additive. The additive did the trick. It swelled all the 30 year old seals, including the rear main seal which was replaced several times. The supercharger no longer leaks. Another seal additive in the PS pump just about eliminated the leaking.

Part of the original problem is that synthetics were only available in a much lower viscosity than what was recommended.
I remember those synthetic tests; probably have it in one of the old mags.
I replaced the engine oil, T5 oil & rear diff oil with Redline. The T5 sure shifted easier.
 
Last edited:

FastDriver

My dad had a bra
SN Certified Technician
Sep 5, 2001
4,543
1,247
214
Fort Knox, KY
Maybe it was just true with earlier ester oils, like it says in the link that JR posted. It did actually support my understanding that it can clear deposits in the seals that open up leaks, though.

I'll tell you guys what. I happen to have recently acquired a higher mileage (at least 167k miles) car that I have relatively little $$$ in. I don't plan to keep it long, and it does not currently leak. I'll switch to Mobil 5W-30 synthetic and report back. Let's put it to the test.
 
Last edited:
  • Like
Reactions: RaggedGT

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
33,092
9,229
224
Massachusetts
I had 100K mile or so on my Fox when I switched to Mobil 1 syn. Like I said, that was 2-3 years ago. I've driven around 1K mile since and and haven't noticed any leakage issues
 

1990 5.0 LX

Member
Apr 11, 2019
37
21
18
70
Ben Lomond, CA
Besides the '90 LX, here are the other older cars I'm using synthetic oil on with no smoking or leaking issues: '95 Lincoln (210K miles), '87 GMC Suburban (230K miles), '69 Galaxie (140K miles) '64 TBird (46K miles). I tend to maintain and hang onto older cars and run them as long as I can.

By the way, the '90 LX with 320K miles runs strong, no smoke, no bad noises. I think these 302s can run almost forever if they're maintained and not abused.
 
  • Agree
Reactions: General karthief

Black GT

Member
Sep 8, 2018
89
5
18
64
Jacksonville, Florida
Now you guys have me afraid to use the mobil 1 full synthetic oil I just bought for a oil change. I got the one for high mileage engines if that makes a difference. The guy I bought the car from last year told me he had just done a full synthetic oil change before I bought the car. I know the oil looked like it was fresh but wonder if he was telling the truth about full synthetic. I have no leaks at all right now.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
16,940
5,415
193
polk county florida
Now you guys have me afraid to use the mobil 1 full synthetic oil I just bought for a oil change. I got the one for high mileage engines if that makes a difference. The guy I bought the car from last year told me he had just done a full synthetic oil change before I bought the car. I know the oil looked like it was fresh but wonder if he was telling the truth about full synthetic. I have no leaks at all right now.
use it. Don't think too much about it. It's a little like tires, it's all in what you do with them, some tires are better in the rain, some are better on the track, they all wear out, so does oil, just change it. I stick with one brand.
I have used wolfs head synthetic blend truck oil in the 'dump truck' (7.3 turbo) for 500,000 miles, it has 585,000 on it and the only leak it has is the dipstick tube at the oil pan. Seepage at the rear main.
Never changed a valve cover gasket, only the crank seal and the oil cooler gaskets been changed.
The products today 'ain't your grandpas' oil.
 

90sickfox

I didn't really have an issue with the stink...
SN Certified Technician
Mar 2, 2015
5,315
4,356
203
42
The machine shop I used to deal with told me that Royal Purple may have been why my 347 lifter broke the keeper and wiped the camshaft. The drivetrain was set up correctly but I over revved. I don't know how they came up with that conclusion. Said something about how the synthetic affected the lifter.

All the racers I now at the drag strip and autox use full synthetic....usually royal purple in all their cars. I use dinosaur oil in my turbo 331...will be switching to part synthetic next oil change.
 
Thread starter Similar threads Forum Replies Date
LILCBRA Oil pan gasket change OR starter replacement in a 302 II 1974 - 1978 Mustang II Talk & Tech 4
92j3ieje8 How many miles is an oil change needed for a v6 o4 mustang? 1996 - 2004 SN95 Mustang -General/Talk- 0
1 Oil change question 1965 - 1973 Classic Mustangs -General/Talk- 4
A Auto Transmission oil change. 2015+ (S550) Mustang -General/Talk 3
C 98 GT - Don't see oil level on the dipstick after an oil change SN95 4.6L Mustang Tech 2
E Oil change for modify GT SN95 4.6L Mustang Tech 2
M Please Help and Advice The Welcome Wagon 4
0 03 Mustang v6 .....Rpm dropping/ New oil Change SN95 V6 Mustang Tech 0
1 Engine 1995 Mustang GT 1994 - 1995 Specific Tech 0
Blucifer99 Engine 1992 mustang oil pan capacity with and without filter change Fox 5.0 Mustang Tech 22
D First oil change? 2015+ (S550) Mustang -General/Talk 10
GrandmasterK Check Oil Light After Oil Change Fox 5.0 Mustang Tech 5
EXTRPR50 Oil Change Mess! Wth?? 2005 - 2009 Specific Tech 7
Sketchy_GT Oil/oil Change Fox 5.0 Mustang Tech 24
Debrajean70 Check Engine Light On 2004 Stang Gt With Low Milage!! The Welcome Wagon 5
D Installing Mgw Shifter And Changing Trans Oil. Can I Do It In My Garage? 2010 - 2014 Specific Tech 6
NJBob Oil Change Indicator 2015+ (S550) Mustang -General/Talk 8
KENS89LX Changing Oil Cooler Adapter Gasket SN95 4.6L Mustang Tech 6
NJBob Oil Change - Does Ford Plug In 2015+ (S550) Mustang -General/Talk 3
O Change Out Distributor Now The Oil Pump Not Working 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 7
Still Bill First Oil Change 2015+ (S550) Mustang -General/Talk 7
M Engine No Oil Pressure 5 Min After Oil Change SN95 4.6L Mustang Tech 5
newedgejay Oil Change. SN95 4.6L Mustang Tech 7
8 Water In Oil After Intake Manifold Gasket Change Fox 5.0 Mustang Tech 4
from6to8 Want To Change Out The Oil Tube..............few Questions 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 0
B 95 3.8l Noise After Oil Change 1994 - 1995 Specific Tech 1
oneslowgt Another Oil Change Question Xd 1994 - 1995 Specific Tech 5
D Heavy Vibration @ 3-3500 After Changing Oil Pump Fox 5.0 Mustang Tech 7
Slo5Oh89 Oil Pan Change. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 16
T Has Anyone Changed The Oil Pan Gasket With Motor Still In The Car? 1994 - 1995 Specific Tech 13
The_Grayt_1 Oil change time for my new 02 GT, time vs mileage on oil changes? SN95 4.6L Mustang Tech 14
D Oil Change 2010 - 2014 Specific Tech 2
Tron84 First Oil Change Filter Dissection Pics 2010 - 2014 Specific Tech 4
D 5.9 Oil Change 2010 - 2014 Specific Tech 7
Tim65GT Changing Oil Pan - Gasket is a PITA Classic Mustang Specific Tech 8
BlackBuggy 5.0 Coyote Oil Change 2010 - 2014 Specific Tech 3
BlackBuggy Coyote 5.0 Oil Change 2005 - 2014 S-197 Mustang -General/Talk- 2
brakeswhatbrake 79 5.0 LX automatic wont start after changing oil pump Fox 5.0 Mustang Tech 3
C Changed my oil today... 1996 - 2004 SN95 Mustang -General/Talk- 4
B How to change your oil with Full Synthetic Oil Classic Mustang Specific Tech 0
B How To Change Your Oil with Full Synthetic Oil SN95 4.6L Mustang Tech 1
Sonic04GT First oil change! What type? 1996 - 2004 SN95 Mustang -General/Talk- 42
B engine knock after oil change Classic Mustang Specific Tech 5
littlechief0 1st oil change on my new 2001 Cobra. Oil questions. SVT Tech Forum 8
VPStang 5% oil life change lige soon 2010 - 2014 Specific Tech 7
russ1979 Help 8.8 rear diff., oil change Fox 5.0 Mustang Tech 3
russ1979 8.8 gear oil change Fox 5.0 Mustang Tech 3
ga289stocker Anyone change oil pressure sending unit??? 2.3L (N/A & Turbo) Tech 6
89hatchlx saleen blower oil change??? 2005 - 2009 Specific Tech 5
Jinx Oil change leads to black exhaust 2005 - 2014 S-197 Mustang -General/Talk- 9
Similar threads