Synthetic Oil in 76 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Paso76GMCstepper · 03-15-2005, 04:58 AM

Ok guys I have a 76 K15 with a 350 motor with maybe 3500 miles on a rebuild. I want to go full synthetic. I have Mobil 1 5W40 in it now. Im thinking of going Royal purple in everything, motor, 4spd, transfer case, front and rear ends.

Which one you recomend and what weight would be great, I know I need 90 weight or so gear oil but what about the motor

Mike76251 · 03-15-2005, 07:24 AM

I went Mobil 1 everything........all except the battery acid!
RP is probably just as good.......who knows?.....

benscool1 · 03-15-2005, 12:06 PM

Amsoil is some really good stuff. First oil company to make synthetic I think. They're a little expensive but its really good stuff. My brother is a dealer, and before that my uncles was, so I guess you'd say my family are 'amsoil purists.

**crossy** · 03-15-2005, 04:35 PM

RP is high- I think because of all the expensive Race cars they sponsor?? not that i don'r like race cars but - I buy amsoil when it's on ebay for BIN prices but i had to use Mobile 1 this time. $5.25 a qt. 10K out of an oil change though. My tranny & rear have it also in the Dodge. My tranny popped a line this winter and I ran it(unknowning) until the tranny wa s slipping like crazy and then finally wouldn't move. I fixed the line, refilled and the $2300 BD tranny is fine . something good to be said for synthetics. DAVE

Tom · 03-17-2005, 12:01 AM

I wouldn't go 10,000miles between oil changes but synthetics are good stuff. I use semi-syn's in my trucks since they get the oil change ever 3000miles regardless. These old type engines leak past the rings more then new ones and dirty up the oil real quick, so keeping that oil in after 3k isen't a great idea IMO. That said my girlfriends 03 civic gets mobil 5w20 sythetic and a change every 6000miles, by 3000miles the oil is only just starting to change color and smell [I do change filters every 3k though]

I also run mobil syn 75-90 gear oil in the differentials.

**crossy** · 03-17-2005, 09:05 AM

I do change the filter at 5K

03-15-2005, 04:58 AM	#1
Paso76GMCstepper Registered User Join Date: Jan 2004 Location: Paso Robles, CA Posts: 347	Synthetic Oil in 76 Ok guys I have a 76 K15 with a 350 motor with maybe 3500 miles on a rebuild. I want to go full synthetic. I have Mobil 1 5W40 in it now. Im thinking of going Royal purple in everything, motor, 4spd, transfer case, front and rear ends. Which one you recomend and what weight would be great, I know I need 90 weight or so gear oil but what about the motor __________________ Tony "Life is a Team Sport" To the memory of the Hendrick Motorsports Plane Crash Victims

03-15-2005, 12:06 PM	#3
benscool1 Registered User Join Date: Mar 2003 Location: Williamsfield, IL Posts: 781	Amsoil is some really good stuff. First oil company to make synthetic I think. They're a little expensive but its really good stuff. My brother is a dealer, and before that my uncles was, so I guess you'd say my family are 'amsoil purists. __________________ Ben 84 C10 Silverado 14 Silverado Z71

03-15-2005, 04:35 PM	#4
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	RP is high- I think because of all the expensive Race cars they sponsor?? not that i don'r like race cars but - I buy amsoil when it's on ebay for BIN prices but i had to use Mobile 1 this time. $5.25 a qt. 10K out of an oil change though. My tranny & rear have it also in the Dodge. My tranny popped a line this winter and I ran it(unknowning) until the tranny wa s slipping like crazy and then finally wouldn't move. I fixed the line, refilled and the $2300 BD tranny is fine . something good to be said for synthetics. DAVE __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

03-17-2005, 12:01 AM	#5
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,748	I wouldn't go 10,000miles between oil changes but synthetics are good stuff. I use semi-syn's in my trucks since they get the oil change ever 3000miles regardless. These old type engines leak past the rings more then new ones and dirty up the oil real quick, so keeping that oil in after 3k isen't a great idea IMO. That said my girlfriends 03 civic gets mobil 5w20 sythetic and a change every 6000miles, by 3000miles the oil is only just starting to change color and smell [I do change filters every 3k though] I also run mobil syn 75-90 gear oil in the differentials. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

03-17-2005, 09:05 AM	#6
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	I do change the filter at 5K __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

03-15-2005, 07:24 AM	#2
Mike76251 Senior Member Join Date: Mar 2003 Posts: 2,499	I went Mobil 1 everything........all except the battery acid! RP is probably just as good.......who knows?.....



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