Motor oil serves to lubricate engines and thus retard engine wear.

Question

Motor oil serves to lubricate engines and thus retard engine wear. A study was conducted to assess the effectiveness of various brands of motor oil by using them in taxicabs over a 6,000-mile test period. All the oils did equally well in retarding wear on pistons and cylinders, the relevant parts of the engine. Hence, cheaper brands of oil are the best buys.

Which one of the following, if true, most weakens the argument?

(A) Cheaper brands of motor oil are often used by knowledgeable automobile mechanics for their own cars.

(B) Tests other than of the ability to reduce engine wear also can reliably gauge the quality of motor oil.

(C) The lubricating properties of all motor oils deteriorate over time, and the rate of deterioration is accelerated by heat.

(D) The engines of some individual cars that have had their oil changed every 3,000 miles, using only a certain brand of oil, have lasted an extraordinarily long time.

(E) Ability to retard engine wear is not the only property of motor oil important to the running of an engine.

Bunuel · Accepted Answer

EXPLANATION FROM Fox LSAT

No, no, no. The study was about a bunch of brands of oil in a 6,000 mile trial, and all the oils did equally well. According to the conclusion, this means the cheapest ones are the best buys. But what if the cheapest ones would wear out completely after 6,001 miles, and the more expensive ones would go for 100,000 miles? Would the cheapest ones still be the “best buys,” if that were true? The question asks us to weaken, so let’s look for exactly that or something else that would make the cheapest oils not look like such a bargain.

A) This would strengthen, if anything. We’re looking for a weakener.

B) Yeah, so what? Maybe those “other tests” would also find no difference between cheap and expensive oils. This can’t be a weakener without more information, so it’s not the answer.

C) This is the same for all oils, so how would it attack just the cheap oils? This is out.

D) This also says nothing about cheap oils vs. expensive oils. No way.

E) OK, this answer is not at all what we were looking for, but I still think it’s the best answer. If there are other properties that are important, then how can we conclude that the cheapest oils are the best? If E is true, then at the very least we can say that we need more information (what are the other properties? how do the cheap oils compare on those properties?) before we can decide whether cheap or expensive oil is the best.

I don’t love it, but I’d have to choose E here.

Nidzo · Answer

A) Strengthens the argument. Incorrect.

B) The quality of the oil is not in question. Incorrect.

C) Irrelevant information for the argument. Incorrect.

D) Information isn't specific enough to be relevant. Incorrect.

E) Weakens the argument as there could be other factors at play where more expensive oil will be of greater benefit. Correct.

Answer E

winterschool · Answer

Motor oil serves to lubricate engines and thus retard engine wear. A study was conducted to assess the effectiveness of various brands of motor oil by using them in taxicabs over a 6,000-mile test period. All the oils did equally well in retarding wear on pistons and cylinders, the relevant parts of the engine. Hence, cheaper brands of oil are the best buys.

Which one of the following, if true, most weakens the argument?

(A) Cheaper brands of motor oil are often used by knowledgeable automobile mechanics for their own cars.  Incorrect

support conclusion

(B) Tests other than of the ability to reduce engine wear also can reliably gauge the quality of motor oil.  Incorrect

may be true but cant weakens conclusion. In other tests cheaper oil can show same effectiveness as high price brands

(C) The lubricating properties of all motor oils deteriorate over time, and the rate of deterioration is accelerated by heat.  Incorrect

true for both type of brands

(D) The engines of some individual cars that have had their oil changed every 3,000 miles, using only a certain brand of oil, have lasted an extraordinarily long time.  Incorrect

dont know which type of brand they used

(E)  Ability to retard engine wear is not the only property of motor oil important to the running of an engine.   Correct

directly weakens study, so conclusion should not be true

100mitra · Answer

Correct option E

Premise : Motor oil serves to lubricate engines and thus retard engine wear. 
 Study Information : A study was conducted 
- to assess the effectiveness of various brands of motor oil 
- by using them in taxicabs over a 6,000-mile test period. 
- All the oils did equally well in retarding wear on pistons and cylinders, the relevant parts of the engine. 
 Conclusion : cheaper brands of oil are the best buys.
 Assumption : Cost is considered more important than quality and performance of Oil

Which one of the following, if true, most weakens the argument?

(A) Cheaper brands of motor oil are often used by 
knowledgeable automobile mechanics for their own cars.
 Wrong:  Mechanic details – irrelevant, Cheaper brand used by mechanic – Strengthen the conclusion.

(B)  Tests other than of the ability  
to reduce engine wear also 
can reliably gauge the quality of motor oil.
 Wrong : Test other than, means more test, demean the passage purpose

(C) The lubricating properties of all motor oils  deteriorate  over time, and 
 the rate of deterioration is  accelerated by heat .
 Wrong:  heat factor – irrelevant, it gives property of oli, that more vehicle run, will generate heat and quality of oil will be worsened.

(D) The engines of  some individual cars  that 
have had their oil changed every 3,000 miles, using only a  certain brand of oil , 
 have lasted  an extraordinarily long time.
 Wrong:  No information about, which kind of quality, cost of oil used to give this performance, general statement.

(E) Ability 
to retard engine wear is   not the only property of   motor oil important 
to the running of an engine.
 Correct:  this raise question on conclusion and assumption, that apart from retarding engine wear, oil has other purpose, which can improve engine life with good quality oil.

sivatx2 · Answer

Apart from lubricating engine & to retard engine wear, what other functions can the cheaper brands of oil does? There could be something additional functions expensive ones support, while cheaper ones might does only one function. We don't know why the other brands are priced higher. Hence anything related to this analysis would be the correct weakening argument.

(A) Cheaper brands of motor oil are often used by knowledgeable automobile mechanics for their own cars. 
 This is a strengthener. Eliminate

(B) Tests other than of the ability to reduce engine wear also can reliably gauge the quality of motor oil. 
 Tests results may be positive/negative or mixed for the cheaper brands. Hence this cannot weaken the argument. Eliminate.

(C) The lubricating properties of all motor oils deteriorate over time, and the rate of deterioration is accelerated by heat. 
 This is completely irrelevant to the argument. Eliminate

(D) The engines of some individual cars that have had their oil changed every 3,000 miles, using only a certain brand of oil, have lasted an extraordinarily long time. 
 "Certain brands", is not clear whether it is just cheaper brands/expensive brands/or mix of both. This will not weaken the argument. Eliminate

(E) Ability to retard engine wear is not the only property of motor oil important to the running of an engine .
 This is exactly our analysis. Hence, E is the correct choice.

Motor oil serves to lubricate engines and thus retard engine wear.

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Motor oil serves to lubricate engines and thus retard engine wear.

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