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Ron, ASE Certified Technician
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95 Geo Prizm (Toyota Corolla): Use oil thickener or thicker

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'95 Geo Prizm (Toyota Corolla): Use oil thickener or thicker oil? 181K miles (1.8 liter, 4-cylinder)
Last oil change, the shop used 1 full qt of Lucas Oil Treatment with Castrol high-mileage 5W-30, to mask the recent (cylinder #2 low compression) problem. Worked fine for 2000 miles, but then I had to add � quart more Lucas (top-off level). Mis-firing symptoms are cough/gag/tug that feels like a giant fish jerking the car- (mainly between 2500 and 3500 rpm, worst in �steady state� cruising.)
Questions: How thick/viscous is the Lucas making the oil?
When Winter hits, how hard will it be to start? (Michigan, USA: parking outside.)
Try 10W-30 or 10W-40 oil instead? (Lucas + high-mileage oil = a $60 oil change). Pennzoil or Valvoline better than Castrol? Other products better than Lucas?
Do I �customize� the blend to the different seasons?
I want to get 20K more miles (2-years) out of this car. Still gets 37mpg, I can't afford to replace now.
Thanks [email protected]
Hello and welcome to Justanswer,

You should be fine to use the thicker oil until winter sets in , once the weather start getting cold you should go back to the 5W30 oil as it will be plenty thick due to the cold nights . All three brands are pretty much the same as far as quality so I would go with the cheaper of the three. So yes if the thicker oil works in the warmer weather continue to customize the blend as you have, but once the night start freezing go back to you 5W30 oil so it does not effect starting .

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Customer: replied 5 years ago.

Thanks. Interesting.

So, is 5W-30 + 1qt. Lucas thicker or thinner overall than just using 10W-40 in Spring/Summer/Fall? I will gladly try it by itself.


And, in your opinion, is Lucas the best oil thickener, or what else do you like better?



Lucas is about the same as 40 weight oil , I would run the 5/30 in the winter and try the 10W-40 in the spring and summer.
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Customer: replied 4 years ago.



Thanks for the info. On my last oil change (last week), I had a different oil shop try their "experimental" compression restoring formula (went into the current oil and circulated for 10 mins at 1500 rpm before draining).
They put in Pennzoil high mileage 10W30. I wound up having to add about 4oz of Lucas to get the misfiring symptom to subside. It had come back. 4oz was enough, without risking too high of oil level.

I will add about 4oz of Lucas every thankful of gasoline; that engine uses 1/2 qt. oil in between oil changes anyways- so
The Lucas top-off will keep the oil level full.
1 quart of Lucas is cheap enough (if I buy it myself). Next summer, I may try using a 10W30/10W40 mix.


Thanks again.



Thank you as well Tom.