Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Should I run synthetic or regular oil in my 91 k5?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Piranha300, Nov 30, 2001.

  1. Piranha300

    Piranha300 Registered Member

    Joined:
    Jul 1, 2001
    Posts:
    45
    Likes Received:
    0
    Location:
    Nebraska
    Right now I'm running mobil 1. Will this cause my engine to leak since it has 160,000 miles on it? Any info on oil would be great. Thanks
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    It will probably leak like a colander.
    I swtiched the Lady's engine over to Syntech for a 2700 mile vacation. The fuel pump seals and the valvecovers were leaking like there was no tomorrow. I'm about to again put the new motor that only hase about $5k on it and run Mobile1 in it. SHe's bad about not letting them warm up so I want to run it in her truck.
    I run Mobile 1 Synthetic in my Supra. The motor has ALL new seals in it excpt one. THe seal in the distributor and it can not be replaced....guess where I have a leak. $200 for a replacement.
    WHat happens on high mile engines is the varnish and crud in the dino oil will cake around old seals. The Synthetic will disolve this crud and the crud may be the only thing keeping it from leaking. The Synthtics are also able to get by seals that Dino oil won't.
    With the miles you got on that motor I would keep it on the Dino unless your ready to reseal the engine if it starts leaking.
    Most say that if the motor has over 50k on it to leave it on the Dino. They also say to run the first 10K on Dino to get the rings broke in.

    Women dig dents and flat paint!
    coloradok5.com/gallery/Grim
    75 Jimmy, Dollar
    Grim-Reaper
     
  3. Wheels

    Wheels 1/2 ton status

    Joined:
    Aug 18, 2000
    Posts:
    638
    Likes Received:
    0
    Location:
    Native Floridian living in Oklahoma, USA
    If you've been running synthetic, shouldn't be a problem. If you just started, then it will work it's way through the old leaks that have been clogged and start some minor leaks. Just the nature of the beast. Synthetic is better than fossil oil just in the molecular structure alone and has a broader temperature range. I've run synthetic in all my vehicles since 1983 and in all gear boxes, diff's, t-cases, etc. my .05.
     
  4. johnny reb

    johnny reb 1/2 ton status

    Joined:
    Mar 6, 2000
    Posts:
    326
    Likes Received:
    0
    Location:
    Pittsburgh, PA
    Search the archives for "synthetic oil." This topic has been discussed extensively in the past. I don't remember the link but if you do the search, you'll find an excellent link that explains all you need to know and more about oil.

    1986 K5, New GM 350, Edelbrock Intake, K&N Air Filter, Flowtech Headers, Dual 3" Exhaust, 33" Pirelli Scorpion AT, 700R4, 3.42 gears
     
  5. Piranha300

    Piranha300 Registered Member

    Joined:
    Jul 1, 2001
    Posts:
    45
    Likes Received:
    0
    Location:
    Nebraska
    Well I put Mobil 1 in it about 10,000 miles ago and now it seems to leak a little. Will these leaks seal up if I put dino oil back in it?
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Didn't read your post real well. Your goingto have to seal it. what was keeping it from leaking the synthetic has disolved. Might as well keep running it. Hopefully the rear main won't start to leak. That's the bogger to replace. Your probably going to have to put on new valve cover seals.

    Women dig dents and flat paint!
    coloradok5.com/gallery/Grim
    75 Jimmy, Dollar
    Grim-Reaper
     

Share This Page