Best additave to clean engine?
#37
First post here, but I've been driving Dodges for a while now (2002 Viper GTS, and now an 05 Ram SRT-10) and thought I'd chime in.
First: octane rating indicates a gasoline's resistance to detonation, i.e. its resistance to exploding. A gasoline with a higher octane rating does not burn any stronger than one with a lower octane rating, or produce more power (in the same engine with the same tune). What it does allow is the use of a higher compression ratio (which will produce more power)--the fuel/air mixture is able to be compressed more without risk of igniting the mixture, and when it is lit it will burn evenly. Most modern engines are equipped with a knock sensor (the Viper car is one notable exception; the Viper truck has one) which will signal the ECU to retard the ignition timing if it detects knock (uneven burn) or detonation (ignition before the spark plug lights). Because of this, it's nearly impossible to damage an engine by running a lower-than-required octane rating, but power output will suffer.
Second: both synthetic and conventional oils contain additives and detergents for preventing carbon buildup and cleaning engine surfaces. Where they differ is in their use of viscosity index improvers (VIIs). VIIs are what make modern oils behave like multiple grades at different temperatures (e.g. a 10 grade at cold temperatures and 40 at operating temperatures, 10W-40). Synthetic base oils are naturally more "flexible" than conventional base oils, and require fewer VIIs to achieve a desired multigrade viscosity. This is important because VIIs eventually break down in the hot, high-pressure environment inside an engine. Synthetic oils effectively stay "good" longer than conventional oils.
If you really want better protection for your engine, look at the amount of additives in your engine oil, particularly zinc diethyldithiophosphate (ZDDP), the primary anti-wear ingredient. Each successive API service classification lowers the allowable amount of ZDDP because of its long-term effects on the precious metals in catalytic converters (currently SM, in effect since Nov. 2004, allows 800ppm). The factory-fill for Viper engines is Mobil1 0W-40, a European passenger-car diesel formula not subject to API certification that contains 1000ppm ZDDP; Mobil1 15W-50 contains 1200ppm. For the best protection, look at diesel truck oils. Since diesels do not use catalytic converters, ZDDP levels have remained higher (as much as 2.5x what it is in passenger car oils), and they contain extra detergents due to their long life-cycle (80,000-100,000 miles).
Sorry for the dissertation.
First: octane rating indicates a gasoline's resistance to detonation, i.e. its resistance to exploding. A gasoline with a higher octane rating does not burn any stronger than one with a lower octane rating, or produce more power (in the same engine with the same tune). What it does allow is the use of a higher compression ratio (which will produce more power)--the fuel/air mixture is able to be compressed more without risk of igniting the mixture, and when it is lit it will burn evenly. Most modern engines are equipped with a knock sensor (the Viper car is one notable exception; the Viper truck has one) which will signal the ECU to retard the ignition timing if it detects knock (uneven burn) or detonation (ignition before the spark plug lights). Because of this, it's nearly impossible to damage an engine by running a lower-than-required octane rating, but power output will suffer.
Second: both synthetic and conventional oils contain additives and detergents for preventing carbon buildup and cleaning engine surfaces. Where they differ is in their use of viscosity index improvers (VIIs). VIIs are what make modern oils behave like multiple grades at different temperatures (e.g. a 10 grade at cold temperatures and 40 at operating temperatures, 10W-40). Synthetic base oils are naturally more "flexible" than conventional base oils, and require fewer VIIs to achieve a desired multigrade viscosity. This is important because VIIs eventually break down in the hot, high-pressure environment inside an engine. Synthetic oils effectively stay "good" longer than conventional oils.
If you really want better protection for your engine, look at the amount of additives in your engine oil, particularly zinc diethyldithiophosphate (ZDDP), the primary anti-wear ingredient. Each successive API service classification lowers the allowable amount of ZDDP because of its long-term effects on the precious metals in catalytic converters (currently SM, in effect since Nov. 2004, allows 800ppm). The factory-fill for Viper engines is Mobil1 0W-40, a European passenger-car diesel formula not subject to API certification that contains 1000ppm ZDDP; Mobil1 15W-50 contains 1200ppm. For the best protection, look at diesel truck oils. Since diesels do not use catalytic converters, ZDDP levels have remained higher (as much as 2.5x what it is in passenger car oils), and they contain extra detergents due to their long life-cycle (80,000-100,000 miles).
Sorry for the dissertation.
#38
#39
As far as oils, if I remember correctly the 5.7 Hemi uses 5W-20 as factory fill (from '05 on). The primary reason for running such a light oil is the increase in engine efficiency, and consequently fuel economy (however slight the real-world advantages). Also, I've read that the cylinder-deactivation system (introduced for 2005) requires a thinner oil to function efficiently. That said, I would stay away from 40 and 50 weight oils (unfortunately ruling out the use of diesel oils with their higher ZDDP content). Any synthetic 20 or 30 weight oil should do fine. Just remember to look at the two numbers separately: a 5W-30 is the same as a 0W-30 is the same as anythingW-30 at operating temperature. At cold temperatures, the 0W will flow better than the 5W which will flow better than a 10W. Choose based on how cold you expect it to get before your next oil change.