i use pennzoil, have for years. if Q.S. was really crap, it would no longer exist. most sludge problems are due to other issues such as the engine not getting to the proper temperature, lack of proper change intervals,ect. filter wise i use motorcraft in the ranger, fram in the S-blazer. both vehicles run the "high milage" 5w30 pennzoil.

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blue streak ( R-140) build-->https://flic.kr/s/aHsmBWXRwL
'93 s/c 4.0 4x4,"the green machine" (retired-r.i.p.)
'92 reg cab longbed 2.3 "polar express" (stolen)
' 97 reg cab 3.0 auto ($500 project truck)-rolled
'94 2wd longbed 2.3 manual trans-"R-140"
pictures--> https://www.flickr.com/photos/154582...h/37156884305/