So my car(94 civic ex) calls for 5w-20 oil but i have a bottle of 5w-30 already sitting at home. Is there any real damage to using the last bit of the 5w-30? i hear that it wont do anything but cause lower gas millage. What are the differences between 5w-20 and 5w-30? All i can think of is the thickness of the oil but 30 would only be a notch more thick than 20.

 

Under the assumption that your 1994 vintage engine has more than say 50,000 miles on it, you won't even notice a blip in fuel economy and the engine won't notice the very slight increase in viscosity when the oil is warm. Long story short, you're good to go to use that oil.

 

You'll be fine to use it. 5w means 5 winter. In other words when it is cold your oil will pump like a single grade motor oil sae 5. the 30 means at 212°F the oil works as a single grade oil of SAE 30.

I like to run 0W-40 fully synthetic. Never had a problem.

 

what motor do you have in a 94 that take's 5w20 ?? i don't think any before a 2001 required 5w20

 

my 94 ex was 5w-30

 

It shouldn't make a difference

 

probably someone who owned the car before put a newer civic (01-05) oil cap on it maybe? which calls for 5w20. you'll be fine 5w30

 

here this the service sticker from my 93 si, same motor as your ex