How much does viscosity matter when topping off?

[desertdude]

We have two oil-burning cars. The Toyota uses 5w30 and the Honda uses 5W-20. Oil consumption in both cars is about 0.5 to 1 quart every 3K miles, and I change the oil every 5K.

There have been times where I have one viscosity in the garage, but not the other. How much does it matter if I use the wrong viscosity?

 

[mclasser]

I'd just top off both with 5w30.

 

[desertdude]

Originally Posted by mclasser
I'd just top off both with 5w30.


Point being, I often have 5W-20 or 5w30 on the shelf, but not always both.

So what should I do?

 

[askani79705]

Buy some 5w30 make up oil. Keep it in stock

 

[PimTac]

5w30.

 

[JamesBond]

For topping off in your situation I would feel comfortable using either oil in either car.

 

[dubber09]

Just use 5w30 in both cars, that's it.
I used 5w30 in both my cars for over 5 years now while both caps say 5w-20, they ran just fine, used Penn Plat which is on thinner side anyway. Using Valvoline Daily Protection (which is semi synth in 5w30 weight) in one and Valvoline HM semi synth in the other but both in 5w30 now.

 

[Ursatdx]

Any oil is better than no oil.

 

[Bud]

Originally Posted by JamesBond
For topping off in your situation I would feel comfortable using either oil in either car.


This

 

[benjy]

using the same brand is recommended by many as the add pack will be similar. i would use 5-30 in both + 10-30 would be even better unless in colder northern cal IMO

 

[Ponchinizo]

Originally Posted by benjy
using the same brand is recommended by many as the add pack will be similar. i would use 5-30 in both + 10-30 would be even better unless in colder northern cal IMO


I bet using the same brand is way more important than the same viscosity.

 

[demarpaint]

Given a choice I'd top both up with 5W30, but to run a half quart to a full quart of either grade for the remaining 2K of an OCI isn't going to matter much.

 

[OilUzer]

Since both cars burn oil, step up a grade when changing oil next time.
Don't worry too much about top ups.

 

[Linctex]

Originally Posted by dubber09
Just use 5w30 in both cars, that's it.


This, 100%

You're in the desert.... heck, just buy 10w30 in bulk and run it in both cars.

There's 0% difference between 5w30 and 10w30 in your climate. None.

 

[Linctex]

Originally Posted by demarpaint
Given a choice I'd top both up with 5W30, but to run a half quart to a full quart of either grade for the remaining 2K of an OCI isn't going to matter much.


Absolutely true.

 

[gfh77665]

Originally Posted by Linctex

You're in the desert.... heck, just buy 10w30 in bulk and run it in both cars.

There's 0% difference between 5w30 and 10w30 in your climate. None.




THIS ^^^

 

[DGXR]

I would tend toward 5w30 for topping off. And I agree it's probably a good idea to simplify by running 5w30 in both vehicles, considering they are both oil burners.

 

[BISCUT]

I'm being honest so please don't destroy me. F150 is 0-20 M1EP Subaru is 5-30 M1EP and top off is often M1 0-40 ... use it for my lawn equip