VW bought my TDi Jetta back. I have several quarts of ATE SL.6 brake fluid left. It is DOT 4 but "low viscosity" per VW spec. Any issue in using it in my 80 series? I know DOT 4 is fine but curious about the low viscosity part. I also realize service intervals on DOT 4 are more frequent than DOT 3, but I change it about once a year anyway. Thanks!