Straight gades for top-offs?

Messages
17,298
Location
OH
While I usually have some of the same oil used at the last change for top-offs on those engines that require them, I also have about 3/4 of a case remaining of RK HD30, bought cheaply on a Thanksgiving Day special a couple of years ago for top-off use. My reasoning is that a straight grade has no VIIs to potentially compound the effects of those already present in the remaining sump oil and that it may provide some useful thickening of what will be oil that's suffered some loss in viscosity in use. A straight SAE 30 might not be the pick in January, but April through October around here it seems like an ideal top-off oil. What do you all think?
 
Messages
2,408
Location
CA
depends on how much you are topping off and how long you intend to keep the oil in service after topoff. i would say if you think the oil has degraded enough to have loss of viscosity that it needs help then it maybe time to change the oil. but if you have oil you need to get rid of,have at it.
 
Last edited:
Messages
36,617
Location
ME
Originally Posted By: bubbatime
You could run straight 30 in the summer in 95% of the cars on the road and the cars would be fine and wouldn't know the difference.
Yup particuarly now when so called straight 30s could probably pass a test for a 10w30 or 15w30 but they market it as straight 30.
 
Messages
2,006
Location
Jacksonville, FL
I'm using my stash of SAE 30 for full oil changes in the summer. My Lexus currently has PYB 30 and the 4Runner has VWB 30. It was 94 here with a low of 68 overnight. I can't see any reason not to use it for make up oil at least 6 months out of the year.
 

fdcg27

Thread starter
Messages
17,298
Location
OH
Without doing the math, I'll hazard that a 30 is probably thinner at 68F than a 0W-20 is at 0F. It certainly wouldn't be any thicker. It kills me how some members can't seem to grasp the significance of temperature in determining viscosity, especially at cold engine start each morning.
 
Messages
43,676
Location
'Stralia
Originally Posted By: FlyNavyP3
I'm using my stash of SAE 30 for full oil changes in the summer. My Lexus currently has PYB 30 and the 4Runner has VWB 30. It was 94 here with a low of 68 overnight. I can't see any reason not to use it for make up oil at least 6 months out of the year.
Very interested in what you've seen with regards to the new "issues" of sluggishness and fuel economy hit with this approach.
 
Messages
2,006
Location
Jacksonville, FL
Shannow, I've only put about 1,000 miles on the 4Runner so far with the SAE 30 but I can't say that there is any indication of perceived "sluggish" engine performance, it builds RPM just like it did with a multi grade oil. Fuel economy is hard to tell as my driving patterns aren't really consistent enough and with the heat of summer building I let it idle more for the AC. It hasn't made any difference that I can't attribute to other factors in fuel economy. The Lexus sees a more regimented commute of 115 miles per day which is 50/50 interstate highway at 75-78 MPH and 55-65 MPH on back roads. I have not seen any change in its fuel economy over the 3,800 miles on it's current fill of SAE 30. The Lexus engine also has oil actuated VVT-I which some people said wouldn't function properly on SAE 30. I didn't believe that since it never exhibited any issues at -20 to -30 F with 5w30 when it lived up north in the winter. The Lexus also has no perceived sluggishness. Both vehicles will be run for 5,000 miles and a UOA performed on them. Hopefully that answers your question! Cheers
 
Top