My 99 consistently went 16k miles (FSS tripped) before oil changes using mostly M1 European Blend 0W/40 (factory fill).

Blackstone tests showed it had 50% of its TBN remaining and almost no fuel, soot or metal contaminants at that mileage.

Mine consumed 1 qt every 8k miles like clockwork.

My miles were mostly highway (80/20), FSS will have a considerably shorter interval if driving mostly city miles and things like shutting down before reaching full operating temp will affect it greatly. Some cars would trip at 5-6k miles. Is all based upon driving style.

I never found any reason not to trust it.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)